Alaunos Therapeutics (TCRT) 10-K 24 Feb 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Feb. 10, 2016	Jun. 30, 2015
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Trading Symbol	ZIOP
Entity Registrant Name	ZIOPHARM ONCOLOGY INC
Entity Central Index Key	1,107,421
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		131,718,579
Entity Public Float			$ 1,293,080,196

BALANCE SHEETS

BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 140,717	$ 42,803
Receivables	446	145
Prepaid expenses and other current assets	11,358	1,139
Total current assets	152,521	44,087
Property and equipment, net	581	531
Deposits	128	128
Other non current assets	494	491
Total assets	153,724	45,237
Current liabilities:
Accounts payable	2,008	2,004
Accrued expenses	8,906	7,182
Deferred revenue - current portion	6,861	1,360
Deferred rent - current portion	348	280
Total current liabilities	18,123	10,826
Deferred revenue, net of current position	47,917
Deferred rent, net of current position	313	570
Total liabilities	$ 66,353	$ 11,396
Commitments and contingencies (note 8)
Stockholders' equity:
Common stock, $0.001 par value; 250,000,000 shares authorized; 131,718,579 and 104,452,105 shares issued and outstanding at December 31, 2015 and 2014, respectively	$ 132	$ 104
Additional paid-in capital - common stock	579,939	406,349
Accumulated Deficit	(492,700)	(372,612)
Total stockholders' equity	87,371	33,841
Total liabilities and stockholders' equity	$ 153,724	$ 45,237

BALANCE SHEETS (Parenthetical)

BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	131,718,579	104,452,105
Common stock, shares outstanding	131,718,579	104,452,105

STATEMENTS OF OPERATIONS

STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Collaboration Revenue	$ 4,332	$ 1,373	$ 800
Operating expenses:
Research and development	106,785	32,706	42,852
General and administrative	17,647	12,166	15,661
Total operating expenses	124,432	44,872	58,513
Loss from operations	(120,100)	(43,499)	(57,713)
Other income (expense), net	12	(5)	(579)
Change in fair value of warrants		11,723	1,185
Net loss	$ (120,088)	$ (31,781)	$ (57,107)
Basic and diluted net loss per share	$ (0.96)	$ (0.31)	$ (0.66)
Weighted average common shares outstanding used to compute basic and diluted net loss per share	125,416,084	101,130,710	85,943,175

STATEMENTS OF CHANGES IN STOCKH

STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Stock Options	Common Stock	Common StockStock Options	Additional Paid-in Capital Common Stock	Additional Paid-in Capital Common StockStock Options	Additional Paid-in Capital Warrants	Accumulated Deficit
Beginning Balance (in shares) at Dec. 31, 2012			83,236,840
Beginning Balance at Dec. 31, 2012	$ 48,445		$ 83		$ 325,177		$ 6,909	$ (283,724)
Stock-based compensation	3,507				3,507
Issuance of common stock, net of commission and expenses of $3,678 (2013) & $6,305 (2015) (in shares)			16,445,000
Issuance of common stock, net of commission and expenses of $3,678 (2013) & $6,305 (2015)	$ 53,880		$ 16		53,864
Exercise of employee stock options (in shares)	570,168			570,168
Exercise of employee stock options		$ 956		$ 1		$ 955
Exercise of warrants to purchase common stock (in shares)	112,808		112,808
Exercise of warrants to purchase common stock	$ 200				396		(196)
Issuance of restricted common stock			75,272
Repurchase of shares of restricted common stock (in shares)			(116,723)
Repurchase of shares of restricted common stock	(498)				(498)
Cancelled/ Forfeiture of unvested restricted common stock			(163,747)
Expired warrants					3,110		(3,110)
Net loss	(57,107)							(57,107)
Ending Balance (in shares) at Dec. 31, 2013			100,159,618
Ending Balance at Dec. 31, 2013	49,383		$ 100		386,511		3,603	(340,831)
Stock-based compensation	$ 4,743				4,743
Exercise of employee stock options (in shares)	613,138			613,138
Exercise of employee stock options		1,386				1,386
Exercise of warrants to purchase common stock (in shares)	3,725,277		3,747,254
Exercise of warrants to purchase common stock	$ 10,654		$ 4		13,963		(3,313)
Issuance of restricted common stock			66,828
Repurchase of shares of restricted common stock (in shares)			(112,333)
Repurchase of shares of restricted common stock	(544)				(544)
Cancelled/ Forfeiture of unvested restricted common stock			(22,400)
Expired warrants					290		(290)
Net loss	(31,781)							(31,781)
Ending Balance (in shares) at Dec. 31, 2014			104,452,105
Ending Balance at Dec. 31, 2014	33,841		$ 104		406,349		$ 0	(372,612)
Stock-based compensation	7,997				7,997
Issuance of common stock, net of commission and expenses of $3,678 (2013) & $6,305 (2015) (in shares)			11,500,000
Issuance of common stock, net of commission and expenses of $3,678 (2013) & $6,305 (2015)	$ 94,320		$ 12		94,309
Exercise of employee stock options (in shares)	3,249,160			2,519,267
Exercise of employee stock options		$ 4,568		$ 3		$ 4,566
Issuance of restricted common stock			1,590,574
Issuance of restricted common stock			$ 2		(2)
Repurchase of shares of restricted common stock (in shares)			(61,819)
Repurchase of shares of restricted common stock	$ (518)				(518)
Repurchase of common stock (Shares)			(3,711)
Repurchase of common stock	(34)				(34)
Issuance of common stock in licensing agreement (in shares)			11,722,163
Issuance of common stock in licensing agreement	67,285		$ 12		67,273
Net loss	(120,088)							(120,088)
Ending Balance (in shares) at Dec. 31, 2015			131,718,579
Ending Balance at Dec. 31, 2015	$ 87,371		$ 132		$ 579,939			$ (492,700)

STATEMENTS OF CHANGES IN STOCK6

STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2013
Issuance of common stock, commissions and expenses	$ 6,305	$ 3,678

STATEMENTS OF CASH FLOWS

STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net loss	$ (120,088)	$ (31,781)	$ (57,107)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	357	462	738
Stock-based compensation	7,997	4,743	3,507
Change in fair value of warrants		(11,723)	(1,185)
Common stock issued in exchange for license agreement	67,285
Loss on disposal of fixed assets			585
(Increase) decrease in:
Receivables	(301)		(87)
Prepaid expenses and other current assets	(10,214)	809	4,964
Other noncurrent assets	(3)	37	477
Increase (decrease) in:
Accounts payable	4	1,582	(1,087)
Accrued expenses	1,724	827	(10,159)
Deferred revenue	53,418	(1,373)	(800)
Deferred rent	(189)	(213)	625
Other noncurrent liabilities		(20)	20
Net cash used in operating activities	(10)	(36,650)	(59,509)
Cash flows from investing activities:
Purchases of property and equipment	(412)	(193)	(132)
Proceeds from sale of property and equipment			1
Net cash used in investing activities	(412)	(193)	(131)
Cash flows from financing activities:
Proceeds from exercise of stock options	4,568	1,386	956
Payments to employees for repurchase of restricted common stock	(518)	(544)	(498)
Proceeds from exercise of warrants		10,600	200
Repurchase of common stock	(34)
Proceeds from issuance of common stock, net	94,320		53,880
Net cash provided by financing activities	98,336	11,442	54,538
Net increase (decrease) in cash and cash equivalents	97,914	(25,401)	(5,102)
Cash and cash equivalents, beginning of period	42,803	68,204	73,306
Cash and cash equivalents, end of period	140,717	42,803	68,204
Supplementary disclosure of cash flow information:
Cash paid for interest	0	0	0
Cash paid for income taxes	0	0	0
Supplementary disclosure of noncash investing and financing activities:
Exercise of equity-classified warrants to common shares		692	$ 196
Issuance of common stock in license agreement	$ 67,285
Exercise of liability-classified warrants to common shares		$ 54

Organization

Organization	12 Months Ended
	Dec. 31, 2015
Organization	1. Organization ZIOPHARM Oncology, Inc., which is referred to as “ZIOPHARM” or the “Company”, is a biopharmaceutical company seeking to acquire, develop and commercialize, on its own or with commercial partners, a diverse portfolio of cancer therapies that address unmet medical needs. The Company’s operations to date have consisted primarily of raising capital and conducting research and development. The Company’s fiscal year ends on December 31. The Company has operated at a loss since its inception in 2003 and has minimal revenues. The Company anticipates that losses will continue for the foreseeable future. At December 31, 2015, the Company’s accumulated deficit was approximately $492.7 million. Given its current development plans, the Company anticipates cash resources will be sufficient to fund operations into the fourth quarter of 2017. The Company’s ability to continue operations after its current cash resources are exhausted depends on its ability to obtain additional financing or to achieve profitable operations, as to which no assurances can be given. Cash requirements may vary materially from those now planned because of changes in the Company’s focus and direction of its research and development programs, competitive and technical advances, patent developments, regulatory changes or other developments. Additional financing will be required to continue operations after the Company exhausts its current cash resources and to continue its long-term plans for clinical trials and new product development. There can be no assurance that any such financing can be obtained by the Company, or if obtained, what the terms thereof may be, or that any amount that the Company is able to raise will be adequate to support the Company’s working capital requirements until it achieves profitable operations.

Financings

Financings	12 Months Ended
	Dec. 31, 2015
Financings	2. Financings On February 3, 2015, the Company entered into an underwriting agreement with J.P. Morgan Securities LLC, as representative of the several underwriters named therein, relating to the issuance and sale of 10,000,000 shares of its common stock. The price to the public in the offering was $8.75 per share, and the underwriters agreed to purchase the shares from the Company pursuant to the underwriting agreement at a purchase price of $8.225 per share. Under the terms of the underwriting agreement, the Company also granted the underwriters an option, exercisable for 30 days, to purchase up to an additional 1,500,000 shares of common stock at a purchase price of $8.225 per share. The offering was made pursuant to the Company’s effective registration statement on Form S-3 (SEC File No. 333-201826) previously filed with the SEC, and a prospectus supplement thereunder. The underwriters purchased the 10,000,000 shares and the additional 1,500,000 shares on February 9 and February 17, 2015, respectively. The net proceeds from the offering were approximately $94.3 million after deducting underwriting discounts and estimated offering expenses paid by the Company. On October 23, 2013, the Company entered into an underwriting agreement with J. P. Morgan Securities LLC, as representative of the several underwriters named therein, relating to the issuance and sale of 14,300,000 shares of its common stock. The price to the public in the offering was $3.50 per share, and the underwriters agreed to purchase the shares from the Company pursuant to the underwriting agreement at a purchase price of $3.29 per share. Under the terms of the underwriting agreement, the Company also granted the underwriters an option, exercisable for 30 days, to purchase up to an additional 2,145,000 shares of common stock at a purchase price of $3.29 per share, and the underwriters elected to exercise such option in full. The offering was made pursuant to the Company’s effective registration statement on Form S-3 (SEC File No. 333-177793) previously filed with the SEC, and a prospectus supplement thereunder. The underwriters purchased the 14,300,000 shares and the additional 2,145,000 shares on October 29, 2013. The net proceeds from the offering were approximately $53.9 million after deducting underwriting discounts and estimated offering expenses paid by the Company.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Summary of Significant Accounting Policies	3. Summary of Significant Accounting Policies Basis of Presentation The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Although the Company regularly assesses these estimates, actual results could differ from those estimates. Changes in estimates are recorded in the period in which they become known. The Company’s most significant estimates and judgments used in the preparation of our financial statements are: • Clinical trial expenses; • Collaboration agreements; • Fair value measurements for stock based compensation and warrants; and • Income taxes. Subsequent Events The Company evaluated all events and transactions that occurred after the balance sheet date through the date of this filing. During this period, the Company did not have any material subsequent events that impacted its financial statements or disclosures. Cash and Cash Equivalents Cash equivalents consist primarily of demand deposit accounts and deposits in short-term U.S. treasury money market mutual funds. Cash equivalents are stated at cost, which approximates fair market value. Concentrations of Credit Risk Financial instruments which potentially subject the Company to concentrations of credit risk consist principally of cash and cash equivalents. The Company maintains cash accounts in commercial banks, which may, at times, exceed federally insured limits. The Company has not experienced any losses in such accounts. The Company believes it is not exposed to any significant credit risk on cash and cash equivalents. Property and Equipment Property and equipment are recorded at cost. Expenditures for maintenance and repairs are charged to expense while the costs of significant improvements are capitalized. Depreciation is provided using the straight-line method over the following estimated useful lives of the related assets, which is between three and five years. Upon retirement or sale, the cost of the assets disposed of and the related accumulated depreciation are eliminated from the balance sheets and related gains or losses are reflected in the statements of operations. Restricted Cash Restricted cash of $388 thousand, which is restricted as collateral for the Company’s facility leases and $104 thousand that is restricted as collateral for a line of credit is included in other assets. Long-Lived Assets The Company reviews the carrying values of its long-lived assets for possible impairment whenever events or changes in circumstances indicate that the carrying amounts of the assets may not be recoverable. Any long-lived assets held for disposal are reported at the lower of their carrying amounts or fair values less costs to sell. Warrants The Company applied the accounting standard which provided guidance in assessing whether an equity-based financial instrument is indexed to an entity’s own stock for purposes of determining whether a financial instrument should be treated as a derivative. In applying the methodology the Company concluded that certain warrants issued by the Company had terms that did not meet the criteria to be considered indexed to the Company’s own stock and therefore were classified as liabilities in the Company’s balance sheet. The liability classified warrants were subject to re-measurement at each balance sheet date and any change in fair value was recognized as a component of “Other income, net” in the accompanying Statement of Operations. Fair value was measured using the binomial valuation model. All warrants expired in December 2014. Fair Value Measurements The Company has certain financial assets and liabilities recorded at fair value which have been classified as Level 1, 2 or 3 within the fair value hierarchy as described in the accounting standards for fair value measurements. • Level 1—Quoted prices in active markets for identical assets or liabilities. • Level 2—Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. • Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Assets and liabilities measured at fair value on a recurring basis as of December 31, 2015 and 2014 are as follows: ($ in thousands) Fair Value Measurements at Reporting Date Using Description Balance as of Quoted Prices in Significant Other Significant Cash equivalents $ 137,405 $ 137,405 $ — $ — ($ in thousands) Fair Value Measurements at Reporting Date Using Description Balance as of Quoted Prices in Significant Other Significant Cash equivalents $ 37,290 $ 37,290 $ — $ — The cash equivalents consist primarily of short term U.S. treasury money market mutual funds which are actively traded. Revenue Recognition from Collaboration Agreements The Company has primarily generated revenue through collaboration arrangements with strategic partners for the development and commercialization of product candidates. The Company recognizes revenue for each unit of accounting when evidence of an arrangement exists, delivery has occurred or services have been rendered, the seller’s price to the buyer is fixed or determinable and collectability is reasonably assured The Company’s collaboration agreements may provide for various types of payments, including upfront payments, funding of research and development, milestone payments, licensing fees and product royalties. The specifics of the Company’s significant agreements are detailed in Note 8, Commitments and Contingencies. The Company considers a variety of factors in determining the appropriate method of accounting for its collaboration agreements, including whether multiple deliverables can be separated and accounted for individually as separate units of accounting. Where there are multiple deliverables within a collaboration agreement that cannot be separated and therefore are combined into a single unit of accounting, revenues are deferred and recognized over the estimated period of performance, which is typically the development term. If the deliverables can be separated, the Company applies the relevant revenue recognition guidance to each individual deliverable. The specific methodology for the recognition of the underlying revenue is determined on a case-by-case basis according to the facts and circumstances applicable to each agreement. Generally, the Company has accounted for its collaboration agreements as a single unit of accounting. Milestone payments are recognized as revenue upon achievement of the milestone only if (1) the milestone payment is non-refundable, (2) substantive effort is involved in achieving the milestone and (3) the amount of the milestone is reasonable in relation to the effort expended or the risk associated with achievement of the milestone. If any of these conditions are not met, the milestone payment is deferred and recognized as revenue over the estimated remaining period of performance under the contract as the Company completes its performance obligations. Royalties are recognized as earned in accordance with the terms of various research and collaboration agreements. Research and Development Costs Research and development expenditures are charged to the statement of operations as incurred. Such costs include proprietary research and development activities, purchased research and development, and expenses associated with research and development contracts, whether performed by the Company or contracted with independent third parties. Income Taxes Income taxes are accounted for under the liability method. Deferred tax assets and liabilities are recognized for the estimated future tax consequences of temporary differences between the financial statement carrying amounts and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the year in which the temporary differences are expected to be recovered or settled. The Company evaluates the realizability of its deferred tax assets and establishes a valuation allowance when it is more likely than not that all or a portion of deferred tax assets will not be realized. The Company accounts for uncertain tax positions using a “more-likely-than-not” threshold for recognizing and resolving uncertain tax positions. The evaluation of uncertain tax positions is based on factors including, but not limited to, changes in tax law, the measurement of tax positions taken or expected to be taken in tax returns, the effective settlement of matters subject to audit, new audit activity and changes in facts or circumstances related to a tax position. The Company evaluates this tax position on an annual basis. The Company also accrues for potential interest and penalties, related to unrecognized tax benefits in income tax expense (see Note 10, Income Taxes). Accounting for Stock-Based Compensation Stock-based compensation cost is measured at the grant date, based on the estimated fair value of the award, and is recognized as expense over the employee’s requisite service period. Stock-based compensation expense is based on the number of awards ultimately expected to vest and is therefore reduced for an estimate of the awards that are expected to be forfeited prior to vesting. Consistent with prior years, the Company uses the Black-Scholes option pricing model which requires estimates of the expected term option holders will retain their options before exercising them and the estimated volatility of the Company’s common stock price over the expected term. The Company recognizes the full impact of its share-based employee payment plans in the statements of operations for each of the years ended December 31, 2015, 2014, and 2013 and did not capitalize any such costs on the balance sheets. The Company recognized $5.3 million, $3.7 million, and $2.3 million of compensation expense related to vesting of stock options during the years ended December 31, 2015, 2014, and 2013, respectively. In the years ended December 31, 2015, 2014, and 2013, the Company recognized $2.7 million, $1.0 million, and $1.2 million of compensation expense, respectively, related to vesting of restricted stock (see Note 12, Stock Option Plan). In the years ended December 31, 2015, 2014, and 2013, the Company recognized $8.0 million, $4.7 million, and $3.5 million of compensation expense, respectively, related to vesting of all employee and director awards. The following table presents share-based compensation expense included in the Company’s Statements of Operations: Year ended December 31, (in thousands) 2015 2014 2013 Research and development $ 1,403 $ 1,416 $ 792 General and administrative 6,594 3,327 2,715 Share based employee compensation expense before tax 7,997 4,743 3,507 Income tax benefit — — — Net share based employee compensation expense $ 7,997 $ 4,743 $ 3,507 The fair value of each stock option is estimated at the date of grant using the Black-Scholes option pricing model. The estimated weighted-average fair value of stock options granted to employees in 2015, 2014, and 2013 was approximately $10.47, $3.58, and $2.51 per share, respectively. Assumptions regarding volatility, expected term, dividend yield and risk-free interest rate are required for the Black-Scholes model. The volatility assumption is based on the Company’s historical experience. The risk-free interest rate is based on a U.S. treasury note with a maturity similar to the option award’s expected life. The expected life represents the average period of time that options granted are expected to be outstanding. The Company calculated expected term using the simplified method described in SEC Staff Accounting Bulletin, or SAB, No. 107 and No. 110 as it continues to meet the requirements promulgated in SAB No. 110. The assumptions for volatility, expected life, dividend yield and risk-free interest rate are presented in the table below: 2015 2014 2013 Weighted average risk-free interest rate 1.46 - 1.93% 1.74 - 2.11% 1.00 - 2.10% Expected life in years 6 6 6 Expected volatility 79.13 - 86.81% 85.22 - 94.55% 83.40 - 95.96% Expected dividend yield 0 0 0 Net Loss Per Share Basic net loss per share is computed by dividing net loss by the weighted average number of common shares outstanding for the period. The Company’s potentially dilutive shares, which include outstanding common stock options, unvested restricted stock and warrants, have not been included in the computation of diluted net loss per share for any of the periods presented as the result would be antidilutive. Such potential common shares at December 31, 2015, 2014, and 2013 consist of the following: December 31, 2015 2014 2013 Stock options 3,481,468 6,505,664 6,747,303 Unvested restricted stock 1,586,388 144,508 352,865 Warrants — — 10,539,767 5,067,856 6,650,172 17,639,935 New Accounting Pronouncements In August 2014, the FASB issued ASU 2014-15, Presentation of Financial Statements—Going Concern In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers

Restructuring

Restructuring	12 Months Ended
	Dec. 31, 2015
Restructuring	4. Restructuring The Company underwent restructuring activities during the year ended December 31, 2013 which included a reduction in workforce and office space, resulting in sublease agreements in Boston and New York. As a result, the Company incurred restructuring charges of $1.7 million, $0.6 million was included in general and administrative expenses and $1.1 million was included in research and development expenses. The Company also incurred charges for exit and disposal activities from the Boston and New York sublease agreements which resulted in an aggregate loss of $0.8 million recorded in general and administrative expenses, and a loss on the disposal of fixed assets of $0.6 million, recorded in Other income in the Statement of Operations for the year ended December 31, 2013. On October 17, 2013, the Company entered into a sublease agreement to lease 7,259 square feet in its New York office to a subtenant. The Company remains primarily liable to pay rent on the original lease. Accordingly, the Company recorded a loss on the sublease in the amount of $729 thousand for the year ended December 31, 2013, representing the remaining contractual obligation of $2.3 million, less $1.6 million in payments from our subtenant. The Company retired assets in this subleased area as a result of this sublease with a net book value of $392 thousand, and recorded a loss on disposal of fixed assets for the same amount for the year ended December 31, 2013. On August 30, 2013, the Company entered into a sublease agreement to lease 5,249 square feet in our Boston office to a subtenant. The Company remains primarily liable to pay rent on the original lease. The Company recorded a loss on the sublease in the amount of $42 thousand for the year ended December 31, 2013, representing the remaining contractual obligation of $367 thousand, less $325 thousand in payments from our subtenant. The Company retired assets in this subleased area as a result of this sublease with a net book value of $194 thousand, and recorded a loss on disposal of fixed assets. The company previously held a security deposit of $20 thousand in accordance with the sublease, which was recorded in other non-current assets and other liabilities on the balance sheet for the year ended December 31, 2013. This sublease tenant vacated the lease in October 2014. On May 22, 2015, the Company subleased previously vacant office space in the Boston Office for approximately $105 thousand for the period of June 2015 through August 2016. We expect to receive a total of $44 thousand in the next year from our subtenant in the Boston Office.

Property and Equipment, net

Property and Equipment, net	12 Months Ended
	Dec. 31, 2015
Property and Equipment, net	5. Property and Equipment, net Property and equipment, net, consists of the following: December 31, (in thousands) 2015 2014 Office and computer equipment $ 1,105 $ 1,094 Software 886 874 Leasehold improvements 990 927 Manufacturing equipment 572 251 3,553 3,146 Less: accumulated depreciation (2,972 ) (2,615 ) Property and equipment, net $ 581 $ 531 Depreciation and amortization charged to the Statement of Operations for the years ended December 31, 2015, 2014, and 2013 was: $358 thousand, $462 thousand and, $738 thousand, respectively.

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2015
Accrued Expenses	6. Accrued Expenses Accrued expenses consist of the following: December 31, (in thousands) 2015 2014 Clinical consulting services $ 2,331 $ 2,802 Preclinical services 3,976 2,027 Employee compensation 1,453 768 Professional services 317 422 Payroll taxes and benefits 289 417 Manufacturing services 253 308 Accrued vacation 221 212 Other consulting services 66 226 Total $ 8,906 $ 7,182

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2015
Related Party Transactions	7. Related Party Transactions On January 6, 2011, the Company entered into an Exclusive Channel Partner Agreement, which is referred to as the Channel Agreement, with Intrexon Corporation, or Intrexon (see Note 8, Commitments and Contingencies). A director of the Company, Randall J. Kirk, is the CEO, a director, and the largest stockholder of Intrexon. On March 27, 2015, the Company and Intrexon entered into a Second Amendment to Exclusive Channel Partner Agreement amending the Channel Agreement, which is referred to as the ECP Amendment. The ECP Amendment modified the scope of the parties’ collaboration under the Channel Agreement in connection with the worldwide License and Collaboration Agreement, or the Ares Trading Agreement, which the Company and Intrexon entered into with Ares Trading S.A., or Ares Trading, on March 27, 2015. The ECP Amendment provided that Intrexon will pay to the Company fifty percent of all payments that Intrexon receives for upfronts, milestones and royalties under the Ares Trading Agreement (see Note 8, Commitments and Contingencies). The Amendment also reduces Intrexon’s aggregate commitment under a Stock Purchase Agreement that the parties executed in connection with the initial Channel Agreement to purchase the Company’s common stock from $50.0 million to $43.5 million, which has been satisfied. On January 13, 2015, the Company, together with Intrexon, entered into a license agreement with MD Anderson, which is referred to as the MD Anderson License. Pursuant to the MD Anderson License, the Company and Intrexon hold an exclusive, worldwide license to certain technologies owned and licensed by MD Anderson including technologies relating to novel CAR+ T cell therapies arising from the laboratory of Laurence Cooper, M.D., Ph.D., the Chief Executive Officer of the Company, formerly a professor of pediatrics at MD Anderson and now currently a visiting scientist under that institution’s policies, as well as either co-exclusive or non-exclusive licenses under certain related technologies. In partial consideration for entering into the MD Anderson License, the Company issued MD Anderson an aggregate of 11,722,163 shares of common stock for which the Company incurred a $67.3 million charge. The Company has determined that the rights acquired in the MD Anderson License represent in-process research and development with no alternative future use. As a result of the common stock issued to MD Anderson in connection with this transaction, MD Anderson became a beneficial holder of more than five percent of the Company’s common stock. (see Note 8, Commitments and Contingencies). During the year ending December 31, 2015, the Company made three quarterly payments totaling an aggregate of $11.25 million under this arrangement. On February 3, 2015, Intrexon purchased 1,440,000 shares of common stock in the Company’s public offering (see Note 2, Financings) upon the same terms as others that participated in the offering. On June 29, 2015, the Company re-purchased 3,711 shares of common stock from Intrexon, at a discount of 5% to the closing price of the Company’s common stock on the date of purchase, which represented fractional shares that resulted from Intrexon’s special stock dividend of the Company’s shares to Intrexon’s shareholders, for $34 thousand. On January 8, 2016, the Company purchased a remaining 168 shares from Intrexon for $2 thousand. During the years ended December 31, 2015, 2014 and 2013, the Company expensed $16.3 million, $12.0 million, and $7.8 million, respectively, for services performed by Intrexon. As of December 31, 2015 and 2014 the Company has recorded $4.6 million and $1.9 million in current liabilities, respectively, for amounts due to Intrexon. On September 28, 2015, the Company, entered into a new Exclusive Channel Collaboration Agreement, or the GvHD Agreement, with Intrexon, whereby the Company will use Intrexon’s technology directed towards in vivo

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies	8. Commitments and Contingencies Operating Leases Prior to December 31, 2012, the Company entered into an operating lease in New York, NY for office space. In accordance with this agreement, the Company entered into a letter of credit in the amount of $388 thousand, naming the Company’s landlord as beneficiary. In January 2012, the Company amended the lease agreement, adding additional office space. The collateral for the letter of credit is restricted cash and recorded in other non-current assets on the balance sheet as of December 31, 2015 and 2014. The lease for office space in New York, NY expires in October 2018. On October 17, 2013, the Company entered into a sublease agreement to lease all of its New York office space to a subtenant. The Company remains primarily liable to pay rent on the original lease. The Company recorded a loss on the sublease in the amount of $729 thousand for the year ended December 31, 2013, representing the remaining contractual obligation of $2.3 million, less $1.6 million in payments from its subtenant. The Company retired assets as a result of this sublease with a net book value of $392 thousand, and recorded a loss on disposal of fixed assets for the same amount for the year ended December 31, 2013. The Company continues to maintain the $388 thousand letter of credit in respect of the New York office space. Prior to December 31, 2012, the Company entered into separate operating lease agreements for various spaces in a building in Boston, MA. In June 2012, the Company re-negotiated a master lease for the entire Boston office space that incorporated all three lease agreements under the same master agreement expiring in August 2016. As of December 31, 2015 and 2014, a total security deposit of $127 thousand is included in deposits on the balance sheet. On August 30, 2013, the Company entered into a sublease agreement to lease a portion of its Boston office to a subtenant. The Company remains liable to pay rent on the original lease. The Company recorded a loss on the sublease in the amount of $42 thousand for the year ended December 31, 2013, representing the remaining contractual obligation of $367 thousand, less $325 thousand in payments from its subtenant. This sublease tenant vacated the leased premises in October 2014. At December 31, 2014, the Company applied the $20 thousand deposit received from the sublease tenant against its outstanding rent obligation. On March 31, 2015, the Company recorded a loss of $167 thousand on the first floor sublease. On May 22, 2015, the Company subleased the vacant office space for approximately $105 thousand for the period of June 2015 through August 2016, and the tenant provided a security deposit of $17 thousand. Since the prior lease obligation has been fully expensed, rent received from the tenant will reduce current rent expense. Future net minimum lease payments under operating leases as of December 31, 2015 are as follows (in thousands): 2016 $ 1,139 2017 928 2018 851 2019 427 2020 and beyond 712 4,057 Less: contractual sublease income (962 ) Future minimum lease payments, net $ 3,095 Total rent expense was approximately $1.0 million, $1.2 million, and $1.0 million for the years ended December 31, 2015, 2014, and 2013. The Company records rent expense on a straight-line basis over the term of the lease. Accordingly, the Company has recorded a liability for deferred rent at December 31, 2015 and 2014 of $661 thousand ($348 thousand current and $313 long-term) and 2014 of $850 thousand ($280 thousand current and $570 long-term) respectively, which is recorded in deferred rent on the balance sheet. License Agreements Exclusive Channel Partner Agreement with Intrexon Corporation for the Cancer Programs On January 6, 2011, the Company entered into an Exclusive Channel Partner Agreement, or the Channel Agreement, with Intrexon that governs a “channel partnering” arrangement in which the Company uses Intrexon’s technology to research, develop and commercialize products in which DNA is administered to humans for expression of anti-cancer effectors for the purpose of treatment or prophylaxis of cancer, which the Company collectively refers to as the Cancer Program. This Channel Agreement establishes committees comprised of representatives of the Company and Intrexon that govern activities related to the Cancer Program in the areas of project establishment, chemistry, manufacturing and controls, clinical and regulatory matters, commercialization efforts and intellectual property. The Channel Agreement grants the Company a worldwide license to use patents and other intellectual property of Intrexon in connection with the research, development, use, importing, manufacture, sale, and offer for sale of products involving DNA administered to humans for expression of anti-cancer effectors for the purpose of treatment or prophylaxis of cancer, which is collectively referred to as the ZIOPHARM Products. Such license is exclusive with respect to any clinical development, selling, offering for sale or other commercialization of ZIOPHARM Products, and otherwise is non-exclusive. Subject to limited exceptions, the Company may not sublicense these rights without Intrexon’s written consent. Under the Channel Agreement, and subject to certain exceptions, the Company is responsible for, among other things, the performance of the Cancer Program, including the development, commercialization and certain aspects of manufacturing of ZIOPHARM Products. Intrexon is responsible for establishing manufacturing capabilities and facilities for the bulk manufacture of products developed under the Cancer Program, certain other aspects of manufacturing and costs of discovery-stage research with respect to platform improvements and costs of filing, prosecution and maintenance of Intrexon’s patents. Subject to certain expense allocations and other offsets provided in the Channel Agreement, the Company will pay Intrexon on a quarterly basis 50% of net profits derived in that quarter from the sale of ZIOPHARM Products, calculated on a ZIOPHARM Product-by- ZIOPHARM Product basis. The Company has likewise agreed to pay Intrexon on a quarterly basis 50% of revenue obtained in that quarter from a sublicensor in the event of a sublicensing arrangement. In addition, in partial consideration for each party’s execution and delivery of the Channel Agreement, the Company entered into a stock purchase agreement with Intrexon. Upon termination of the Channel Agreement, the Company may continue to develop and commercialize any ZIOPHARM Product that, at the time of termination: • Is being commercialized by the Company; • Has received regulatory approval; • Is a subject of an application for regulatory approval that is pending before the applicable regulatory authority; or • Is the subject of at least an ongoing Phase 2 clinical trial (in the case of a termination by Intrexon due to an uncured breach or a voluntary termination by the Company), or an ongoing Phase 1 clinical trial in the field (in the case of a termination by the Company due to an uncured breach or a termination by Intrexon following an unconsented assignment by the Company or its election not to pursue development of a Superior Therapy (as defined in the Channel Agreement)). The Company’s obligation to pay 50% of net profits or revenue described above with respect to these “retained” products will survive termination of the Channel Agreement. On March 27, 2015, the Company and Intrexon entered into an Exclusive Channel Partner Amendment, or ECP Amendment, amending the Channel Agreement. The ECP Amendment modifies the scope of the parties’ collaboration under the Channel Agreement in connection with the Ares Trading Agreement discussed below. Pursuant to the ECP Amendment, the chimeric antigen receptor T cell products to be developed and commercialized pursuant to the Ares Trading Agreement shall be included within the Intrexon/ZIOPHARM collaboration under the Channel Agreement. The ECP Amendment provides that Intrexon will pay to the Company fifty percent of all payments Intrexon receives for upfronts, milestones and royalties under the Ares Trading Agreement. Exclusive Channel Collaboration Agreement with Intrexon Corporation for Graft-Versus-Host Disease On September 28, 2015, the Company, entered into a new Exclusive Channel Collaboration Agreement, or the GvHD Agreement, with Intrexon, whereby the Company will use Intrexon’s technology directed towards in vivo L. lactis The GvHD Agreement grants the Company a worldwide license to use specified patents and other intellectual property of Intrexon in connection with the research, development, use, importing, manufacture, sale, and offer for sale of products developed under the GvHD Program, or the Products. Such license is exclusive with respect to any clinical development, selling, offering for sale or other commercialization of the Products, and otherwise is non-exclusive. Subject to limited exceptions, the Company may not sublicense the rights described without Intrexon’s written consent. Under the GvHD Agreement, and subject to certain exceptions, the Company is responsible for, among other things, the performance of the GvHD Program including development, commercialization and certain aspects of manufacturing of the Products. Among other things, Intrexon is responsible for the costs of establishing manufacturing capabilities and facilities for the bulk manufacture of the Products, certain other aspects of manufacturing, costs of discovery-stage research with respect to platform improvements and costs of filing, prosecution and maintenance of Intrexon’s patents. The Company paid Intrexon a technology access fee of $10 million in cash in October 2015 and will reimburse Intrexon for all research and development costs. Subject to certain expense allocations and other offsets provided in the GvHD Agreement, the GvHD Agreement also provides for equal sharing of the profits derived from the sale of the Products. During the first 24 months after September 28, 2015, the GvHD Agreement may be terminated by (i) either party in the event of a material breach by the other, except for the failure of the other party to use diligent efforts or to comply with any diligence obligations set forth in the GvHD Agreement and (ii) Intrexon under certain circumstances if the Company assigns its rights under the GvHD Agreement without Intrexon’s consent. Following such twenty-four month period, Intrexon may also terminate the GvHD Agreement if the Company elects not to pursue the development of the GvHD Program identified by Intrexon that is a “Superior Therapy,” as such term is defined in the GvHD Agreement. Also following such period, the Company may voluntarily terminate the GvHD Agreement upon 90 days’ written notice to Intrexon. Upon termination of the GvHD Agreement, the Company may continue to develop and commercialize any Product that, at the time of termination: • is being commercialized by the Company, • has received regulatory approval, • is a subject of an application for regulatory approval that is pending before the applicable regulatory authority, or • is the subject of at least an ongoing Phase 2 clinical trial (in the case of a termination by Intrexon due to a Company uncured breach or a voluntary termination by the Company), or an ongoing Phase 1 clinical trial (in the case of a termination by the Company due to an Intrexon uncured breach or a termination by Intrexon following an unconsented assignment by the Company or the Company’s election not to pursue development of a Superior Therapy). The Company’s obligation to pay 50% of net profits or revenue with respect to these “retained” products will survive termination of the GvHD Agreement. The Company has determined that the rights acquired in the GvHD Agreement represent in-process research and development with no alternative future use. Accordingly, the Company recorded a charge of $10.0 million to research and development expense in 2015. License Agreement—The University of Texas MD Anderson Cancer Center On January 13, 2015, the Company, together with Intrexon, entered into a License Agreement, or the MD Anderson License, with The University of Texas MD Anderson Cancer Center, or MD Anderson. Pursuant to the MD Anderson License, the Company and Intrexon hold an exclusive, worldwide license to certain technologies owned and licensed by MD Anderson including technologies relating to novel chimeric antigen receptor (CAR) T cell therapies, non-viral gene transfer systems, genetic modification and/or propagation of immune cells and other cellular therapy approaches, Natural Killer, or NK Cells and T cell receptors, or TCR’s arising from the laboratory of Laurence Cooper, M.D., Ph.D., who became the Chief Executive Officer of the Company on May 7, 2015 and was formerly a tenured professor of pediatrics at MD Anderson and now currently a visiting scientist under that institution’s policies, as well as either co-exclusive or non-exclusive licenses under certain related technologies. Pursuant to the terms of the MD Anderson License, MD Anderson received consideration consisting of $50 million in shares of the Company’s common stock (or 10,124,561 shares), and $50 million in shares of Intrexon’s common stock, in each case based on a trailing 20 day volume weighted average of the closing price of the Company’s and Intrexon’s common stock ending on the date prior to the announcement of the entry into the MD Anderson License, collectively referred to as the License Shares, pursuant to the terms of the License Shares Securities Issuance Agreement described below. The License Shares were issued to MD Anderson on March 11, 2015 pursuant to the terms of the MD Anderson License. On January 9, 2015, in order to induce MD Anderson to enter into the MD Anderson License on an accelerated schedule, the Company and Intrexon entered into a letter agreement, or the Letter Agreement, pursuant to which MD Anderson received consideration of $7.5 million in shares of the Company’s common stock (or 1,597,602 shares), and $7.5 million in shares of Intrexon’s common stock, in each case based on a trailing 20 day volume weighted average of the closing price of the Company’s and Intrexon’s common stock ending on the date prior to the execution of the Letter Agreement, collectively referred to as the Incentive Shares, in the event that the MD Anderson License was entered into on or prior to 8:00 am Pacific Time on January 14, 2015. The Incentive Shares were issued to MD Anderson on March 11, 2015 pursuant to the terms of the Incentive Shares Securities Issuance Agreement described below. On August 17, 2015, the Company, Intrexon and MD Anderson entered into a research and development agreement, or the Research and Development Agreement, to formalize the scope and process for the transfer by MD Anderson, pursuant to the terms of the MD Anderson License, of certain existing research programs and related technology rights, as well as the terms and conditions for future collaborative research and development of new and ongoing research programs. Pursuant to the Research and Development Agreement, the Company, Intrexon and MD Anderson have agreed to form a joint steering committee that will oversee and manage the new and ongoing research programs. As provided under the MD Anderson License, the Company will provide funding for research and development activities in support of the research programs under the Research and Development Agreement for a period of three years and in an amount of no less than $15 million and no greater than $20 million per year. During the year ended December 31, 2015, the Company made three quarterly payments totaling an aggregate of $11.25 million under this arrangement. As of December 31, 2015, MD Anderson has used $911 thousand to offset costs incurred pursuant to the MD Anderson License and the Research and Development Agreement. The net balance of $10.3 million is included in other current assets at December 31, 2015. The term of the MD Anderson License expires on the last to occur of (a) the expiration of all patents licensed thereunder, or (b) the twentieth anniversary of the date of the License; provided, however, that following the expiration of the term of the MD Anderson License, the Company and Intrexon shall then have a fully-paid up, royalty free, perpetual, irrevocable and sublicensable license to use the licensed intellectual property thereunder. After ten years from the date of the MD Anderson License and subject to a 90-day cure period, MD Anderson will have the right to convert the MD Anderson License into a non-exclusive license if the Company and Intrexon are not using commercially reasonable efforts to commercialize the licensed intellectual property on a case-by-case basis. After five years from the date of the MD Anderson License and subject to a 180-day cure period, MD Anderson will have the right to terminate the MD Anderson License with respect to specific technology(ies) funded by the government or subject to a third party contract if the Company and Intrexon are not meeting the diligence requirements in such funding agreement or contract, as applicable. MD Anderson may also terminate the agreement with written notice upon material breach by the Company and Intrexon, if such breach has not been cured within 60 days of receiving such notice. In addition, the MD Anderson License will terminate upon the occurrence of certain insolvency events for both the Company and Intrexon and may be terminated by the mutual written agreement of the Company, Intrexon and MD Anderson. In connection with the License and the issuance of the License Shares and the Incentive Shares, on January 13, 2015, the Company and MD Anderson entered into a Registration Rights Agreement, or the Registration Rights Agreement, pursuant to which the Company agreed to file a “resale” registration statement, or the Registration Statement, registering the resale of the License Shares, the Incentive Shares and any other shares of the Company’s common stock held by MD Anderson on the date that the Registration Statement is filed Under the Registration Rights Agreement, the Company is obligated to maintain the effectiveness of the Registration Statement until all securities therein are sold or are otherwise can be sold pursuant to Rule 144, without any restrictions. A prospectus supplement under the Company’s already effective registration statement on Form S-3 (File No. 333-201826), was filed on April 1, 2015 in satisfaction of the Company’s obligations under the Registration Rights Agreement. The Company has determined that the rights acquired in the MD Anderson License represent in process research and development with no alternative future use. Accordingly, the Company recorded a charge of $67.3 million to research and development expense, as included in the statement of operations for the year ended December 31, 2015, representing the fair value of the 11,722,163 shares of its common stock on the date the MD Anderson License was executed. Ares Trading License and Collaboration Agreement On March 27, 2015, the Company and Intrexon signed a worldwide License and Collaboration Agreement, or the Ares Trading Agreement, with Ares Trading S.A. or “Ares Trading”, a subsidiary of the biopharmaceutical business of Merck KGaA, Darmstadt, Germany, through which the parties established a collaboration for the research and development and commercialization of certain products for the prophylactic, therapeutic, palliative or diagnostic use for cancer in humans. Under the collaboration, Ares Trading will elect CAR-T targets, of which two have been selected during 2015, and for which Ares Trading will provide certain research funding. The Company is responsible for certain research and development expenditures. Once these candidates reach investigational new drug (IND) stage, the programs will be transferred to Ares Trading for clinical development and commercialization. The Company expects to perform multiple preclinical development programs, each consisting of the development of one product candidate, pursuant to the agreement. The Company and Intrexon will also independently conduct research and development on other CAR-T candidates, with Ares Trading having the opportunity during clinical development to opt-in. Intrexon is entitled to receive $5.0 million payable in equal quarterly installments over two years for each identified product candidate, which will be used to fund discovery work. The Company will be responsible for costs exceeding the quarterly installments and all other costs of the preclinical research and development. Ares Trading paid a non-refundable upfront fee of $115.0 million to Intrexon as consideration for entry into the Ares Trading Agreement. Pursuant to the ECP Amendment, the Company was entitled to receive 50% of the upfront fee, or $57.5 million, which we received from Intrexon in July 2015. The Ares Trading Agreement provides for up to $413.0 million of potential payments for certain development and commercial milestones for each product candidate, and royalties ranging from the lower-single digits to the low-teens of net sales derived from the sale of products developed under agreement. The Ares Trading Agreement also provides for up to $50.0 million of payments upon the achievement of certain technical milestones. Intrexon will pay 50% of all milestone and royalty payments that it receives under the Ares Trading Agreement to the Company pursuant to the ECP Amendment. The term of the Ares Trading Agreement commenced in May 2015 and may be terminated by either party in the event of a material breach as defined in the agreement and may be terminated voluntarily by Ares Trading upon 90 days written notice to the Company. The Company considered FASB Accounting Standards Codification 605-25, Multiple-Element Arrangements License Agreements with DEKK-Tec, Inc. and Southern Research Institute On October 15, 2004, the Company entered into a license agreement with DEKK-Tec, Inc., or DEKK-Tec, pursuant to which it was granted an exclusive, worldwide license for palifosfamide. All of the Company’s rights and obligations under the DEKK-Tec license agreement was assigned to Predictive Therapeutics, Ltd., in the first quarter of 2016, with the exception of the Company’s obligation under a stock option to acquire 13,808 shares of the Company’s common stock at an exercise price of $0.02 per share, which remains outstanding in accordance with the terms. On February 5, 2007, the Company exercised an option to enter into an exclusive license agreement with Southern Research Institute, or SRI, for certain isophosphoramide mustard analogs. Under the license agreement, the Company was required to remit minimum annual royalty payments of $25 thousand until the first commercial sale of a licensed product. These payments were made for the years ended December 31, 2015, 2014, and 2013. All of the Company’s remaining obligations under the SRI license agreement were assigned to Predictive Therapeutics, Ltd., in the first quarter of 2016. License Agreement with Predictive Therapeutics, Ltd. On November 12, 2015, the Company entered into a License Agreement with Predictive Therapeutics, Ltd., or Predictive. Pursuant to the License Agreement, the Company granted Predictive an exclusive license to develop and commercialize palifosfamide. In exchange, the Company received an upfront payment of $250 thousand and is entitled to receive additional payments of up to $12.8 million in development-and sales-based milestones, single digit royalty payments on net sales of palifosfamide, once commercialized, and a percentage of any sublicense revenues generated by Predictive. Predictive will be responsible for all costs related to the development, manufacturing and commercialization of palifosfamide. The $250 thousand upfront payment received in November 2015 is being amortized over the period of the Company’s research and development effort related to transitional services. There are certain deliverables that are included in the License Agreement including transfer of intellectual property and prior research and development results, which are estimated by management to be completed by June 30, 2016. Accordingly, the Company has recorded $50 thousand in revenue during the twelve months ended December 31, 2015. The remaining deferred revenue balance of $200 thousand at December 31, 2015 has been classified as current. In accordance with the License Agreement with Predictive, the Company is no longer obligated to continue their research and development efforts beyond the transitional services. In the first quarter of 2016, all of the Company’s rights and obligations under the DEKK-Tec and SRI license agreements were assigned to Predictive Therapeutics, Ltd., with the exception of the Company’s obligation to DEKK-Tec under a stock option to acquire 13,808 shares of the Company’s common stock at an exercise price of $0.02 per share, which remains outstanding in accordance with the terms. Patent and Technology License Agreement—The University of Texas MD Anderson Cancer Center and the Texas A&M University System. On August 24, 2004, the Company entered into a patent and technology license agreement with MD Anderson, which the Company refers to, collectively, as the Licensors. Under this agreement, the Company was granted an exclusive, worldwide license to rights (including rights to U.S. and foreign patent and patent applications and related improvements and know-how) for the manufacture and commercialization of two classes of organic arsenicals (water- and lipid-based) for human and animal use. The class of water-based organic arsenicals includes darinaparsin. The Company issued options to purchase 50,222 shares outside of the Company’s stock option plans following the successful completion of certain clinical milestones, of which 37,666 have vested. The remaining 12,556 shares will vest upon enrollment of the first patient in a multi-center pivotal clinical trial i.e. a human clinical trial intended to provide the substantial evidence of efficacy necessary to support the filing of an approvable New Drug Application, or NDA. In addition, the Licensors are entitled to receive certain milestone payments. The Company may be required to make additional payments upon achievement of certain other milestones in varying amounts which on a cumulative basis could total up to an additional $4.5 million. In addition, the Licensors are entitled to receive single digit percentage royalty payments on sales from a licensed product and will also be entitled to receive a portion of any fees that the Company may receive from a possible sublicense under certain circumstances. Collaboration Agreement with Solasia Pharma K.K. On March 7, 2011, the Company entered into a License and Collaboration Agreement with Solasia Pharma K.K., or Solasia. Pursuant to the License and Collaboration Agreement, the Company granted Solasia an exclusive license to develop and commercialize darinaparsin in both IV and oral forms and related organic arsenic molecules, in all indications for human use in a pan- Asian/Pacific territory comprised of Japan, China, Hong Kong, Macau, Republic of Korea, Taiwan, Singapore, Australia, New Zealand, Malaysia, Indonesia, Philippines and Thailand. As consideration for the license, the Company received an upfront payment of $5.0 million to be used exclusively for further clinical development of darinaparsin outside of the pan-Asian/Pacific territory, and will be entitled to receive additional payments of up to $32.5 million in development-based milestones and up to $53.5 million in sales-based milestones. The Company will also be entitled to receive double digit royalty payments from Solasia based upon net sales of licensed products in the applicable territories, once commercialized, and a percentage of sublicense revenues generated by Solasia. Under the License and Collaboration Agreement, the Company provided Solasia with drug product to conduct clinical trials. These transfers were accounted for as a reduction of research and development costs and an increase in collaboration receivables. The agreement provides that Solasia will be responsible for the development and commercialization of darinaparsin in the pan-Asian/Pacific territory. On July 31, 2014, the Company entered into an amendment and restatement of the License and Collaboration Agreement granting Solasia an exclusive worldwide license to develop and commercialize darinaparsin, and related organoarsenic molecules, in both intravenous and oral forms in all indications for human use. In exchange, the Company will be eligible to receive from Solasia development-and sales-based milestones, a royalty on net sales of darinaparsin, once commercialized, and a percentage of any sublicense revenues generated by Solasia. Solasia will be responsible for all costs related to the development, manufacturing and commercialization of darinaparsin. The Company’s Licensors, as defined in the agreement, will receive a portion of all milestone and royalty payments made by Solasia to the Company in accordance with the terms of the Company’s license agreement with the Licensors. The $5.0 million upfront payment received in March 2011 is being amortized over the period of the Company’s research and development effort. The Company originally estimated this period to be 75 months. In accordance with the amended and restated License and Collaboration Agreement with Solasia, the Company is no longer obligated to continue their research and development efforts in connection with the upfront payment. However, there are certain deliverables that are included in the amended and restated License and Collaboration Agreement including transfer of intellectual property and prior research and development results, which were originally estimated by management to be completed by March 31, 2015 when the amended and restated License and Collaboration Agreement was signed in July 2014. Management subsequently reassessed the period of performance related to the remaining transitional services to be completed under the amended and restated License and Collaboration Agreement and determined that the services are now expected to be completed by March 31, 2016. Accordingly, the Company has recorded $1.1 million in revenue during the twelve months ended December 31, 2015. The remaining deferred revenue balance of $272 thousand at December 31, 2015 has been classified as current. License Agreement with Baxter Healthcare Corporation On November 3, 2006, the Company entered into a definitive Asset Purchase Agreement for indibulin and a License Agreement to proprietary nanosuspension technology with affiliates of Baxter Healthcare S.A. The purchase included the entire indibulin intellectual property portfolio as well as existing drug substance and capsule inventories. The terms of the Asset Purchase Agreement included an upfront cash payment and an additional payment for existing inventory. During each of the years ended December 31, 2015, 2014, and 2013, the installment of $250 thousand were paid and expensed. CRO Services Agreement with Novella Clinical, Inc. On December 4, 2008, the Company entered into a Master Clinical Research Organization Services Agreement with Novella Clinical, Inc., or Novella, under which Novella provides clinical research organization, or CRO, services in support of the Company’s clinical trials. The work order for the newest trial being conducted by Novella was signed on November 2, 2012. Novella was entitled to cumulative payments of up to $790 thousand under these arrangements, which is payable in varying amounts upon Novella achieving specified milestones. On August 18, 2014 and November 6, 2014, the Company signed two respective amendments of the Master Clinical Research Organization Services Agreement with Novella. The amendments reflect the removal of data management, statistical and clinical study report services, as well as a change in the timeline and scope of clinical trial support. During the year ended December 31, 2014, three clinical milestones were met and expensed totaling $236 thousand. The remaining milestone of $10 thousand was met and expensed during the quarter ended March 31, 2015. There are no remaining obligations under this agreement.

Warrants

Warrants	12 Months Ended
	Dec. 31, 2015
Warrants	9. Warrants The Company has issued both warrants that are accounted for as liabilities and warrants that are accounted for as equity instruments. The Company follows accounting standards that provide guidance in assessing whether an equity-issued financial instrument is indexed to an entity’s own stock for purposes of determining whether a financial instrument should be treated as a derivative and classified as a liability. Accounting standards require that liability classified warrants be recorded at their fair value at each financial reporting period and the resulting gain or loss be recorded as other income (expense) in the Statements of Operations. Fair value is measured using the binomial valuation model. Liability-Classified Warrants In connection with a December 2009 public offering, the Company issued warrants to purchase an aggregate of 8,206,520 shares of common stock, including the investor warrants and 464,520 warrants issued to the Underwriters. The warrants had a 5 year term and expired in December 2014. Subject to certain exceptions, these warrants provided anti-dilution protection in the event the Company should subsequently issue common stock or common stock equivalents at a price less than the exercise price of the warrants then in effect. The Company assessed whether the Warrants required accounting as derivatives. The Company determined that the warrants were not indexed to the Company’s own stock in accordance with FASB Accounting Standards Codification, Derivatives and Hedging On December 31, 2013, the liability-classified warrants were valued at $11.8 million using a Binomial/Monte Carlo valuation model. The decrease in the fair value of the warrant liabilities of $1.2 million for the year ended December 31, 2013 was recorded as Other income, net in the Statements of Operations. In December 2014, the company recognized a gain of $195 thousand on the expiration of liability-classified warrants. The following pricing assumptions were used in the Binomial/Monte Carlo valuation model at December 31, 2013: December 31, Risk-free interest rate 0.13 % Expected life in years 0.94 Expected volatility 80 % Expected dividend yield 0 In connection with its 2009 private placement, the Company issued warrants to purchase an aggregate of 2,910,954 shares of common stock (including 138,617 warrants issued to the placement agents) which were exercisable immediately. The warrants had an exercise price of $2.04 per share and a 5 year term. The fair value of the warrants was estimated at $4.2 million using a Black-Scholes model with the following assumptions: expected volatility of 105%, risk free interest rate of 2.41%, expected life of 5 years and no dividends. The fair value of the warrants was recorded in the equity section of the balance sheet. In October 2009, 136,986 of these warrants were exercised. During 2013 135,346 warrants were exercised for 112,808 shares of common stock. Of these warrants, all 135,346 were equity-classified; there were no liability-classified warrants exercised. During 2014 4,004,907 warrants were exercised for 3,725,277 shares of common stock. Of these warrants, 2,249,062 were equity-classified and 1,755,845 were liability-classified warrants. Additionally, 12,329 equity-classified warrants and 6,479,231 liability-classified warrants expired without being exercised. All remaining warrants have expired during the year ended December 31, 2014 and none are outstanding as of December 31, 2015.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Taxes	10. Income Taxes There is no provision for income taxes because the Company has incurred operating losses since inception. The reported amount of income tax expense for the years differs from the amount that would result from applying domestic federal statutory tax rates to pretax losses primarily because of the changes in the valuation allowance. Significant components of the Company’s deferred tax assets at December 31, 2015 and 2014 are as follows: December 31, (in thousands) 2015 2014 Net operating loss carryforwards $ 96,215 $ 79,050 Start-up and organizational costs 64,942 38,562 Research and development credit carryforwards 29,564 26,112 Stock compensation 1,997 1,181 Capitalized acquisition costs 10,429 11,376 Deferred revenue 2,695 534 Depreciation 251 208 Other 1,673 1,547 207,766 158,570 Less valuation allowance (207,766 ) (158,570 ) Effective tax rate $ — $ — Deferred income taxes reflect the net tax effects of temporary differences between the carrying amount of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. At December 31, 2015, the Company has aggregate net operating loss carryforwards for federal tax purposes of approximately $251 million available to offset future federal taxable income to the extent permitted under the Internal Revenue Code, or IRC, expiring in varying amounts through 2034. Additionally, the Company has approximately $29 million of research and development credits at December 31, 2015, expiring in varying amounts through 2034, which may be available to reduce future taxes. Under the IRC Section 382, certain substantial changes in the Company’s ownership may limit the amount of net operating loss carryforwards that can be utilized in any one year to offset future taxable income. The net operating loss carryforwards for the year ended December 31, 2015 includes approximately $10.2 million resulting from excess tax deductions from stock options. Pursuant to ASC 740, the deferred tax asset relating to excess tax benefits generated from exercises of stock options was not recognized for financial statement purposes. Section 382 of the IRC provides limits to which a corporation that has undergone a change in ownership (as defined) can utilize any net operating loss, or NOL, and general business tax credit carryforwards it may have. The Company commissioned an analysis to determine whether Section 382 could limit the use of its carryforwards in this manner. After completing the analysis, it was determined an ownership change had occurred in February 2007. As a result of this change, the Company’s NOL’s and general business tax credits from February 23, 2007 and prior would be completely limited under IRC Section 382. The deferred tax assets related to NOL’s and general business credits have been reduced by $11.2 million and $636 thousand, respectively, as a result of the change. The Company updated the IRC Section 382 analysis through December 31, 2014. It was determined a change of ownership occurred on February 28, 2011. The Company’s NOL’s were not further limited as a result of the change. The Company has provided a valuation allowance for the full amount of these net deferred tax assets, since it is more likely than not that these future benefits will not be realized. However, these deferred tax assets may be available to offset future income tax liabilities and expenses. The valuation allowance increased by $49.2 million in 2015 primarily due to net operating loss carryforwards and the increase in research and development credits. Income taxes using the federal statutory income tax rate differ from the Company’s effective tax rate primarily due to the change in the valuation allowance on deferred tax assets. A reconciliation of income tax expense (benefit) at the statutory federal income tax rate and income taxes as reflected in the financial statements is as follows: Year Ended December 31, (in thousands) 2015 2014 2013 Federal income tax at statutory rates 34 % 34 % 34 % State income tax, net of federal tax benefit 5 % 2 % 4 % Research and development credits 3 % 3 % 9 % Stock compensation -1 % -4 % -2 % Other 0 % -4 % 1 % Increase in valuation allowance -41 % -31 % -46 % Effective tax rate 0 % 0 % 0 % The Company adopted ASC740, “Accounting for Uncertain Tax Positions” on January 1, 2007. ASC740 clarifies the accounting for uncertainty in income taxes recognized in an enterprise’s financial statements in accordance with FASB Statement No. 109, “Accounting for Income Taxes.” ASC 740 prescribes a recognition threshold and measurement of a tax position taken or expected to be taken in a tax return. The Company did not establish any additional reserves for uncertain tax liabilities upon adoption of ASC 740. A summary of the company’s adjustments to its uncertain tax positions in the years ended December 31, 2015, 2014, and 2013 are as follows: (in thousands) Balance at December 31, 2012 $ 275 Increase/Decrease for tax positions related to the current year — Increase/Decrease for tax positions related to prior years (37 ) Decrease for settlements with applicable taxing authorities — Decrease for lapses of statute of limitations — Balance at December 31, 2013 $ 238 Increase/Decrease for tax positions related to the current year — Increase/Decrease for tax positions related to prior years — Decrease for settlements with applicable taxing authorities — Decrease for lapses of statute of limitations — Balance at December 31, 2014 $ 238 Increase/Decrease for tax positions related to the current year — Increase/Decrease for tax positions related to prior years — Decreases for settlements with applicable taxing authorities — Decrease for previous year’s lapses of statute of limitations (20 ) Decrease for impact of §382 limitations (218 ) Decrease for lapses of statute of limitations — Balance at December 31, 2015 $ — The Company has not recognized any interest and penalties in the statement of operations because of the Company’s net operating losses and tax credits that are available to be carried forward. When necessary, the Company will account for interest and penalties related to uncertain tax positions as part of its provision for federal and state income taxes. The Company does not expect the amounts of unrecognized benefits will change significantly within the next twelve months. The Company is currently open to audit under the statute of limitations by the Internal Revenue Service and state jurisdictions for the years ended December 31, 1999 through 2015.

Preferred Stock and Stockholder

Preferred Stock and Stockholders' Equity	12 Months Ended
	Dec. 31, 2015
Preferred Stock and Stockholders' Equity	11. Preferred Stock and Stockholders’ Equity On April 26, 2006, the date of the Company’s annual stockholders meeting that year, the shareholders approved the adoption of an Amended and Restated Certificate of Incorporation pursuant to which the Company has 280,000,000 shares of authorized capital stock, of which 250,000,000 shares are designated as common stock (par value $.001 per share), and 30,000,000 shares are designated as preferred stock (par value $.001 per share), which the Company refers to as the Preferred Stock. Common Stock On October 29, 2013, pursuant to an underwriting agreement between the Company and J. P. Morgan Securities LLC, as representative of the several underwriters named therein, the Company completed the sale of an aggregate 16,445,000 shares of the Company’s common stock at a price of $3.50 per share in a public offering. The total gross proceeds resulting from this public offering were approximately $57.6 million, before deducting selling commissions and expenses (see Note 2, Financings). On February 3, 2015, the Company entered into an underwriting agreement with J.P. Morgan Securities LLC, as representative of the several underwriters named therein, relating to the issuance and sale of 10,000,000 shares of our common stock. The price to the public in the offering was $8.75 per share, and the underwriters agreed to purchase the shares from the Company pursuant to the underwriting agreement at a purchase price of $8.225 per share. Under the terms of the underwriting agreement, the Company also granted the underwriters an option, exercisable for 30 days, to purchase up to an additional 1,500,000 shares of common stock at a purchase price of $8.225 per share. The offering was made pursuant to the Company’s effective registration statement on Form S-3 (SEC File No. 333-201826) previously filed with the SEC, and a prospectus supplement thereunder. The underwriters purchased the 10,000,000 shares and the additional 1,500,000 shares on February 9 and 17, 2015, respectively. The net proceeds from the offering were approximately $94.3 million after deducting underwriting discounts and estimated offering expenses paid by the Company. On January 13, 2015, the Company, together with Intrexon, entered into the MD Anderson License. Pursuant to the terms of the MD Anderson License, MD Anderson received consideration of 11,722,163 shares of the Company’s common stock (see Note 8, Commitments and Contingencies). Preferred Stock The Company’s Board of Directors are authorized to designate any series of Preferred Stock, to fix and determine the variations in relative rights, preferences, privileges and restrictions as between and among such series.

Stock Option Plan

Stock Option Plan	12 Months Ended
	Dec. 31, 2015
Stock Option Plan	12. Stock Option Plan The Company adopted the 2003 Stock Option Plan, or the 2003 Plan, in 2003, and it was approved by the Company’s stockholders on December 21, 2004. Upon approval of the 2012 Equity Incentive Plan, no additional stock awards may be granted under the 2003 Plan. The Company adopted the 2012 Equity Incentive Plan, or the 2012 Plan, in May 2012, under which the Company initially reserved for the issuance of 4,000,000 shares of its common stock. The 2012 Plan was approved by the Company’s stockholders on June 20, 2012. On June 18, 2014, the date of the Company’s annual stockholders meeting, the Company’s stockholders approved an amendment to the 2012 Plan increasing the total shares reserved by 5,000,000 shares, for a total of 9,000,000 shares. As of December 31, 2015, the Company had outstanding options issued to its employees to purchase up to 2,420,801 shares of the Company’s common stock, to its directors to purchase up to 927,500 shares of the Company’s common stock, as well as options to consultants in connection with services rendered to purchase up to 133,167 shares of the Company’s common stock. Stock options to employees generally vest ratably over three years and have contractual terms of ten years. Stock options to directors generally vest ratably over one or three years and have contractual terms of ten years. Stock options are valued using the Black-Scholes option pricing model and compensation is recognized based on such fair value over the period of vesting on a straight-line basis. The Company has also reserved an aggregate of 26,364 additional shares for issuance under options granted outside of the 2003 Stock Option Plan. Proceeds from the option exercises during the years ended December 31, 2015, 2014, and 2013 amounted to $4.6 million, $1.4 million and $956 thousand respectively. The intrinsic value of these options amounted to $23.8 million, $2.6 million and $1.4 million for years ended December 31, 2015, 2014 and 2013, respectively. Transactions under the Plan for the years ending December 31, 2015, 2014, and 2013 were as follows: (in thousands, except share and per share data) Number of Weighted- Weighted- Aggregate Outstanding, December 31, 2012 7,147,303 $ 4.11 Granted 2,649,900 3.28 Exercised (570,168 ) 1.68 Cancelled (2,479,732 ) 4.58 Outstanding, December 31, 2013 6,747,303 3.81 Granted 1,099,300 4.95 Exercised (613,138 ) 2.26 Cancelled (727,801 ) 4.54 Outstanding, December 31, 2014 6,505,664 4.07 Granted 427,800 10.47 Exercised (3,249,160 ) 3.95 Cancelled (202,835 ) 4.36 Outstanding, December 31, 2015 3,481,469 $ 4.96 6.98 $ 12,601 Vested and unvested expected to vest at December 31, 2015 3,443,414 $ 4.24 5.84 $ 12,463 Options exercisable, December 31, 2015 2,120,834 $ 4.24 5.84 $ 8,622 Options exercisable, December 31, 2014 3,781,162 $ 4.10 5.80 $ 4,130 Options available for future grant 2,768,230 At December 31, 2015, total unrecognized compensation costs related to non-vested stock options outstanding amounted to $5.3 million. The cost is expected to be recognized over a weighted-average period of 1.55 years. Restricted Stock In May, June and December 2015, the Company issued 1,000,000, 50,000 and 403,083 shares of restricted stock to its employees, respectively, which vest ratably in annual installments over three years, commencing on the first anniversary of the grant date. In September and December 2015, the Company issued 4,186 and 133,305 shares of restricted stock to its non-employee directors, which vest in their entirety at December 31, 2015 and on the one year anniversary of the grant date respectively. In December 2014, the Company issued 66,828 shares of restricted stock to its non-employee directors, which vest in their entirety on the one year anniversary of the grant date. In December 2013, the Company issued 75,272 shares of restricted stock to its non-employee directors, which vested in their entirety on the one year anniversary of the grant date. In September and December 2015, the Company repurchased 7,669 and 16,709 shares at average prices of $11.57 and $8.31, respectively to cover payroll taxes. In January, February and December 2014, the Company repurchased 16,031, 14,600 and 81,702 shares at average prices of $4.37, $4.40 and $5.04 per share, respectively, to cover payroll taxes. In January, March, May and December 2013, the Company repurchased 52,018, 5,400, 2,623, and 56,683 shares at average prices of $4.28, $4.50, $1.65 and $4.37 per share, respectively, to cover payroll taxes. A summary of the status of non-vested restricted stock as of December 31, 2015, 2014 and 2013 is as follows: Number of Shares Weighted-Average Non-vested, December 31, 2012 733,739 $ 4.37 Granted 75,272 4.34 Vested (292,399 ) 4.31 Cancelled (163,747 ) 4.42 Non-vested, December 31, 2013 352,865 4.38 Granted 66,828 5.07 Vested (253,835 ) 4.38 Cancelled (21,350 ) 4.41 Non-vested, December 31, 2014 144,508 4.70 Granted 1,590,574 9.01 Vested (148,694 ) 4.88 Cancelled — — Non-vested, December 31, 2015 1,586,388 $ 9.00 As of December 31, 2015, there was $12.1 million of total unrecognized stock-based compensation expense related to non-vested restricted stock arrangements. The expense is expected to be recognized over a weighted-average period of 1.73 years.

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2015
Employee Benefit Plan	13. Employee Benefit Plan The Company sponsors a qualified 401(k) Retirement Plan under which employees are allowed to contribute certain percentages of their pay, up to the maximum allowed under Section 401(k) of the IIRC. The Company may make contributions to this plan at its discretion. The Company contributed approximately $47 thousand, $79 thousand, and $139 thousand to this plan during the years ended December 31, 2015, 2014, and 2013, respectively.

Selected Quarterly Information

Selected Quarterly Information (Unaudited)	12 Months Ended
	Dec. 31, 2015
Selected Quarterly Information (Unaudited)	14. Selected Quarterly Information (Unaudited) (in thousands, except per share amount) Year Ended December 31, 2015 First Second Third Fourth Revenue $ 272 $ 272 $ 1,869 $ 1,919 Total operating expenses 78,499 14,497 20,035 11,401 Loss from operations (78,227 ) (14,225 ) (18,166 ) (9,482 ) Change in fair value of warrants — — — — Net (loss) (78,231 ) (14,211 ) (18,170 ) (9,476 ) Loss per share, basic and diluted $ (0.69 ) $ (0.11 ) $ (0.14 ) $ (0.07 ) Year Ended December 31, 2014 First Second Third Fourth Revenue $ 200 $ 200 $ 633 $ 340 Total operating expenses 9,984 11,377 12,575 10,936 Loss from operations (9,784 ) (11,177 ) (11,942 ) (10,596 ) Change in fair value of warrants 82 5,600 5,847 194 Net (loss) (9,711 ) (5,576 ) (6,093 ) (10,401 ) Loss per share, basic and diluted $ (0.10 ) $ (0.06 ) $ (0.06 ) $ (0.09 )

Summary of Significant Accoun22

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Basis of Presentation	Basis of Presentation The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”).
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Although the Company regularly assesses these estimates, actual results could differ from those estimates. Changes in estimates are recorded in the period in which they become known. The Company’s most significant estimates and judgments used in the preparation of our financial statements are: • Clinical trial expenses; • Collaboration agreements; • Fair value measurements for stock based compensation and warrants; and • Income taxes.
Subsequent Events	Subsequent Events The Company evaluated all events and transactions that occurred after the balance sheet date through the date of this filing. During this period, the Company did not have any material subsequent events that impacted its financial statements or disclosures.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash equivalents consist primarily of demand deposit accounts and deposits in short-term U.S. treasury money market mutual funds. Cash equivalents are stated at cost, which approximates fair market value.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments which potentially subject the Company to concentrations of credit risk consist principally of cash and cash equivalents. The Company maintains cash accounts in commercial banks, which may, at times, exceed federally insured limits. The Company has not experienced any losses in such accounts. The Company believes it is not exposed to any significant credit risk on cash and cash equivalents.
Property and Equipment	Property and Equipment Property and equipment are recorded at cost. Expenditures for maintenance and repairs are charged to expense while the costs of significant improvements are capitalized. Depreciation is provided using the straight-line method over the following estimated useful lives of the related assets, which is between three and five years. Upon retirement or sale, the cost of the assets disposed of and the related accumulated depreciation are eliminated from the balance sheets and related gains or losses are reflected in the statements of operations.
Restricted Cash	Restricted Cash Restricted cash of $388 thousand, which is restricted as collateral for the Company’s facility leases and $104 thousand that is restricted as collateral for a line of credit is included in other assets.
Long-Lived Assets	Long-Lived Assets The Company reviews the carrying values of its long-lived assets for possible impairment whenever events or changes in circumstances indicate that the carrying amounts of the assets may not be recoverable. Any long-lived assets held for disposal are reported at the lower of their carrying amounts or fair values less costs to sell.
Warrants	Warrants The Company applied the accounting standard which provided guidance in assessing whether an equity-based financial instrument is indexed to an entity’s own stock for purposes of determining whether a financial instrument should be treated as a derivative. In applying the methodology the Company concluded that certain warrants issued by the Company had terms that did not meet the criteria to be considered indexed to the Company’s own stock and therefore were classified as liabilities in the Company’s balance sheet. The liability classified warrants were subject to re-measurement at each balance sheet date and any change in fair value was recognized as a component of “Other income, net” in the accompanying Statement of Operations. Fair value was measured using the binomial valuation model. All warrants expired in December 2014.
Fair Value Measurements	Fair Value Measurements The Company has certain financial assets and liabilities recorded at fair value which have been classified as Level 1, 2 or 3 within the fair value hierarchy as described in the accounting standards for fair value measurements. • Level 1—Quoted prices in active markets for identical assets or liabilities. • Level 2—Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. • Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Assets and liabilities measured at fair value on a recurring basis as of December 31, 2015 and 2014 are as follows: ($ in thousands) Fair Value Measurements at Reporting Date Using Description Balance as of Quoted Prices in Significant Other Significant Cash equivalents $ 137,405 $ 137,405 $ — $ — ($ in thousands) Fair Value Measurements at Reporting Date Using Description Balance as of Quoted Prices in Significant Other Significant Cash equivalents $ 37,290 $ 37,290 $ — $ — The cash equivalents consist primarily of short term U.S. treasury money market mutual funds which are actively traded.
Revenue Recognition	Revenue Recognition from Collaboration Agreements The Company has primarily generated revenue through collaboration arrangements with strategic partners for the development and commercialization of product candidates. The Company recognizes revenue for each unit of accounting when evidence of an arrangement exists, delivery has occurred or services have been rendered, the seller’s price to the buyer is fixed or determinable and collectability is reasonably assured The Company’s collaboration agreements may provide for various types of payments, including upfront payments, funding of research and development, milestone payments, licensing fees and product royalties. The specifics of the Company’s significant agreements are detailed in Note 8, Commitments and Contingencies. The Company considers a variety of factors in determining the appropriate method of accounting for its collaboration agreements, including whether multiple deliverables can be separated and accounted for individually as separate units of accounting. Where there are multiple deliverables within a collaboration agreement that cannot be separated and therefore are combined into a single unit of accounting, revenues are deferred and recognized over the estimated period of performance, which is typically the development term. If the deliverables can be separated, the Company applies the relevant revenue recognition guidance to each individual deliverable. The specific methodology for the recognition of the underlying revenue is determined on a case-by-case basis according to the facts and circumstances applicable to each agreement. Generally, the Company has accounted for its collaboration agreements as a single unit of accounting. Milestone payments are recognized as revenue upon achievement of the milestone only if (1) the milestone payment is non-refundable, (2) substantive effort is involved in achieving the milestone and (3) the amount of the milestone is reasonable in relation to the effort expended or the risk associated with achievement of the milestone. If any of these conditions are not met, the milestone payment is deferred and recognized as revenue over the estimated remaining period of performance under the contract as the Company completes its performance obligations. Royalties are recognized as earned in accordance with the terms of various research and collaboration agreements.
Research and Development Costs	Research and Development Costs Research and development expenditures are charged to the statement of operations as incurred. Such costs include proprietary research and development activities, purchased research and development, and expenses associated with research and development contracts, whether performed by the Company or contracted with independent third parties.
Income Taxes	Income Taxes Income taxes are accounted for under the liability method. Deferred tax assets and liabilities are recognized for the estimated future tax consequences of temporary differences between the financial statement carrying amounts and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the year in which the temporary differences are expected to be recovered or settled. The Company evaluates the realizability of its deferred tax assets and establishes a valuation allowance when it is more likely than not that all or a portion of deferred tax assets will not be realized. The Company accounts for uncertain tax positions using a “more-likely-than-not” threshold for recognizing and resolving uncertain tax positions. The evaluation of uncertain tax positions is based on factors including, but not limited to, changes in tax law, the measurement of tax positions taken or expected to be taken in tax returns, the effective settlement of matters subject to audit, new audit activity and changes in facts or circumstances related to a tax position. The Company evaluates this tax position on an annual basis. The Company also accrues for potential interest and penalties, related to unrecognized tax benefits in income tax expense (see Note 10, Income Taxes).
Accounting for Stock-Based Compensation	Accounting for Stock-Based Compensation Stock-based compensation cost is measured at the grant date, based on the estimated fair value of the award, and is recognized as expense over the employee’s requisite service period. Stock-based compensation expense is based on the number of awards ultimately expected to vest and is therefore reduced for an estimate of the awards that are expected to be forfeited prior to vesting. Consistent with prior years, the Company uses the Black-Scholes option pricing model which requires estimates of the expected term option holders will retain their options before exercising them and the estimated volatility of the Company’s common stock price over the expected term. The Company recognizes the full impact of its share-based employee payment plans in the statements of operations for each of the years ended December 31, 2015, 2014, and 2013 and did not capitalize any such costs on the balance sheets. The Company recognized $5.3 million, $3.7 million, and $2.3 million of compensation expense related to vesting of stock options during the years ended December 31, 2015, 2014, and 2013, respectively. In the years ended December 31, 2015, 2014, and 2013, the Company recognized $2.7 million, $1.0 million, and $1.2 million of compensation expense, respectively, related to vesting of restricted stock (see Note 12, Stock Option Plan). In the years ended December 31, 2015, 2014, and 2013, the Company recognized $8.0 million, $4.7 million, and $3.5 million of compensation expense, respectively, related to vesting of all employee and director awards. The following table presents share-based compensation expense included in the Company’s Statements of Operations: Year ended December 31, (in thousands) 2015 2014 2013 Research and development $ 1,403 $ 1,416 $ 792 General and administrative 6,594 3,327 2,715 Share based employee compensation expense before tax 7,997 4,743 3,507 Income tax benefit — — — Net share based employee compensation expense $ 7,997 $ 4,743 $ 3,507 The fair value of each stock option is estimated at the date of grant using the Black-Scholes option pricing model. The estimated weighted-average fair value of stock options granted to employees in 2015, 2014, and 2013 was approximately $10.47, $3.58, and $2.51 per share, respectively. Assumptions regarding volatility, expected term, dividend yield and risk-free interest rate are required for the Black-Scholes model. The volatility assumption is based on the Company’s historical experience. The risk-free interest rate is based on a U.S. treasury note with a maturity similar to the option award’s expected life. The expected life represents the average period of time that options granted are expected to be outstanding. The Company calculated expected term using the simplified method described in SEC Staff Accounting Bulletin, or SAB, No. 107 and No. 110 as it continues to meet the requirements promulgated in SAB No. 110. The assumptions for volatility, expected life, dividend yield and risk-free interest rate are presented in the table below: 2015 2014 2013 Weighted average risk-free interest rate 1.46 - 1.93% 1.74 - 2.11% 1.00 - 2.10% Expected life in years 6 6 6 Expected volatility 79.13 - 86.81% 85.22 - 94.55% 83.40 - 95.96% Expected dividend yield 0 0 0
Net Loss Per Share	Net Loss Per Share Basic net loss per share is computed by dividing net loss by the weighted average number of common shares outstanding for the period. The Company’s potentially dilutive shares, which include outstanding common stock options, unvested restricted stock and warrants, have not been included in the computation of diluted net loss per share for any of the periods presented as the result would be antidilutive. Such potential common shares at December 31, 2015, 2014, and 2013 consist of the following: December 31, 2015 2014 2013 Stock options 3,481,468 6,505,664 6,747,303 Unvested restricted stock 1,586,388 144,508 352,865 Warrants — — 10,539,767 5,067,856 6,650,172 17,639,935
New Accounting Pronouncements	New Accounting Pronouncements In August 2014, the FASB issued ASU 2014-15, Presentation of Financial Statements—Going Concern In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers

Summary of Significant Accoun23

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Assets and Liabilities Measured at Fair Value on Recurring Basis	Assets and liabilities measured at fair value on a recurring basis as of December 31, 2015 and 2014 are as follows: ($ in thousands) Fair Value Measurements at Reporting Date Using Description Balance as of Quoted Prices in Significant Other Significant Cash equivalents $ 137,405 $ 137,405 $ — $ — ($ in thousands) Fair Value Measurements at Reporting Date Using Description Balance as of Quoted Prices in Significant Other Significant Cash equivalents $ 37,290 $ 37,290 $ — $ —
Share-Based Compensation Expense Included in Statements of Operations	The following table presents share-based compensation expense included in the Company’s Statements of Operations: Year ended December 31, (in thousands) 2015 2014 2013 Research and development $ 1,403 $ 1,416 $ 792 General and administrative 6,594 3,327 2,715 Share based employee compensation expense before tax 7,997 4,743 3,507 Income tax benefit — — — Net share based employee compensation expense $ 7,997 $ 4,743 $ 3,507
Assumptions for Volatility, Expected life, Dividend Yield and Risk-free Interest Rate	The assumptions for volatility, expected life, dividend yield and risk-free interest rate are presented in the table below: 2015 2014 2013 Weighted average risk-free interest rate 1.46 - 1.93% 1.74 - 2.11% 1.00 - 2.10% Expected life in years 6 6 6 Expected volatility 79.13 - 86.81% 85.22 - 94.55% 83.40 - 95.96% Expected dividend yield 0 0 0
Potentially Dilutive Shares Excluded from Computation of Diluted Net Loss Per Share	The Company’s potentially dilutive shares, which include outstanding common stock options, unvested restricted stock and warrants, have not been included in the computation of diluted net loss per share for any of the periods presented as the result would be antidilutive. Such potential common shares at December 31, 2015, 2014, and 2013 consist of the following: December 31, 2015 2014 2013 Stock options 3,481,468 6,505,664 6,747,303 Unvested restricted stock 1,586,388 144,508 352,865 Warrants — — 10,539,767 5,067,856 6,650,172 17,639,935

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	12 Months Ended
	Dec. 31, 2015
Component of Property and Equipment, Net	Property and equipment, net, consists of the following: December 31, (in thousands) 2015 2014 Office and computer equipment $ 1,105 $ 1,094 Software 886 874 Leasehold improvements 990 927 Manufacturing equipment 572 251 3,553 3,146 Less: accumulated depreciation (2,972 ) (2,615 ) Property and equipment, net $ 581 $ 531

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2015
Component of Accrued Expenses	Accrued expenses consist of the following: December 31, (in thousands) 2015 2014 Clinical consulting services $ 2,331 $ 2,802 Preclinical services 3,976 2,027 Employee compensation 1,453 768 Professional services 317 422 Payroll taxes and benefits 289 417 Manufacturing services 253 308 Accrued vacation 221 212 Other consulting services 66 226 Total $ 8,906 $ 7,182

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Future Net Minimum Lease Payments under Operating Leases	Future net minimum lease payments under operating leases as of December 31, 2015 are as follows (in thousands): 2016 $ 1,139 2017 928 2018 851 2019 427 2020 and beyond 712 4,057 Less: contractual sublease income (962 ) Future minimum lease payments, net $ 3,095

Warrants (Tables)

Warrants (Tables)	12 Months Ended
	Dec. 31, 2015
Assumptions Used in Binomial and Monte Carlo Valuation Model	The following pricing assumptions were used in the Binomial/Monte Carlo valuation model at December 31, 2013: December 31, Risk-free interest rate 0.13 % Expected life in years 0.94 Expected volatility 80 % Expected dividend yield 0

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Significant Component of Deferred Tax Assets	Significant components of the Company’s deferred tax assets at December 31, 2015 and 2014 are as follows: December 31, (in thousands) 2015 2014 Net operating loss carryforwards $ 96,215 $ 79,050 Start-up and organizational costs 64,942 38,562 Research and development credit carryforwards 29,564 26,112 Stock compensation 1,997 1,181 Capitalized acquisition costs 10,429 11,376 Deferred revenue 2,695 534 Depreciation 251 208 Other 1,673 1,547 207,766 158,570 Less valuation allowance (207,766 ) (158,570 ) Effective tax rate $ — $ —
Reconciliation of Income Tax Expense (Benefit)	A reconciliation of income tax expense (benefit) at the statutory federal income tax rate and income taxes as reflected in the financial statements is as follows: Year Ended December 31, (in thousands) 2015 2014 2013 Federal income tax at statutory rates 34 % 34 % 34 % State income tax, net of federal tax benefit 5 % 2 % 4 % Research and development credits 3 % 3 % 9 % Stock compensation -1 % -4 % -2 % Other 0 % -4 % 1 % Increase in valuation allowance -41 % -31 % -46 % Effective tax rate 0 % 0 % 0 %
Summary of Adjustments to Uncertain Tax Position	A summary of the company’s adjustments to its uncertain tax positions in the years ended December 31, 2015, 2014, and 2013 are as follows: (in thousands) Balance at December 31, 2012 $ 275 Increase/Decrease for tax positions related to the current year — Increase/Decrease for tax positions related to prior years (37 ) Decrease for settlements with applicable taxing authorities — Decrease for lapses of statute of limitations — Balance at December 31, 2013 $ 238 Increase/Decrease for tax positions related to the current year — Increase/Decrease for tax positions related to prior years — Decrease for settlements with applicable taxing authorities — Decrease for lapses of statute of limitations — Balance at December 31, 2014 $ 238 Increase/Decrease for tax positions related to the current year — Increase/Decrease for tax positions related to prior years — Decreases for settlements with applicable taxing authorities — Decrease for previous year’s lapses of statute of limitations (20 ) Decrease for impact of §382 limitations (218 ) Decrease for lapses of statute of limitations — Balance at December 31, 2015 $ —

Stock Option Plan (Tables)

Stock Option Plan (Tables)	12 Months Ended
	Dec. 31, 2015
Transaction under Stock Option Plan	Transactions under the Plan for the years ending December 31, 2015, 2014, and 2013 were as follows: (in thousands, except share and per share data) Number of Weighted- Weighted- Aggregate Outstanding, December 31, 2012 7,147,303 $ 4.11 Granted 2,649,900 3.28 Exercised (570,168 ) 1.68 Cancelled (2,479,732 ) 4.58 Outstanding, December 31, 2013 6,747,303 3.81 Granted 1,099,300 4.95 Exercised (613,138 ) 2.26 Cancelled (727,801 ) 4.54 Outstanding, December 31, 2014 6,505,664 4.07 Granted 427,800 10.47 Exercised (3,249,160 ) 3.95 Cancelled (202,835 ) 4.36 Outstanding, December 31, 2015 3,481,469 $ 4.96 6.98 $ 12,601 Vested and unvested expected to vest at December 31, 2015 3,443,414 $ 4.24 5.84 $ 12,463 Options exercisable, December 31, 2015 2,120,834 $ 4.24 5.84 $ 8,622 Options exercisable, December 31, 2014 3,781,162 $ 4.10 5.80 $ 4,130 Options available for future grant 2,768,230
Summary of Nonvested Restricted Stock	A summary of the status of non-vested restricted stock as of December 31, 2015, 2014 and 2013 is as follows: Number of Shares Weighted-Average Non-vested, December 31, 2012 733,739 $ 4.37 Granted 75,272 4.34 Vested (292,399 ) 4.31 Cancelled (163,747 ) 4.42 Non-vested, December 31, 2013 352,865 4.38 Granted 66,828 5.07 Vested (253,835 ) 4.38 Cancelled (21,350 ) 4.41 Non-vested, December 31, 2014 144,508 4.70 Granted 1,590,574 9.01 Vested (148,694 ) 4.88 Cancelled — — Non-vested, December 31, 2015 1,586,388 $ 9.00

Selected Quarterly Informatio30

Selected Quarterly Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2015
Selected Quarterly Information	Year Ended December 31, 2015 First Second Third Fourth Revenue $ 272 $ 272 $ 1,869 $ 1,919 Total operating expenses 78,499 14,497 20,035 11,401 Loss from operations (78,227 ) (14,225 ) (18,166 ) (9,482 ) Change in fair value of warrants — — — — Net (loss) (78,231 ) (14,211 ) (18,170 ) (9,476 ) Loss per share, basic and diluted $ (0.69 ) $ (0.11 ) $ (0.14 ) $ (0.07 ) Year Ended December 31, 2014 First Second Third Fourth Revenue $ 200 $ 200 $ 633 $ 340 Total operating expenses 9,984 11,377 12,575 10,936 Loss from operations (9,784 ) (11,177 ) (11,942 ) (10,596 ) Change in fair value of warrants 82 5,600 5,847 194 Net (loss) (9,711 ) (5,576 ) (6,093 ) (10,401 ) Loss per share, basic and diluted $ (0.10 ) $ (0.06 ) $ (0.06 ) $ (0.09 )

Organization - Additional Infor

Organization - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Nature Of Operations [Line Items]
Accumulated Deficit	$ (492,700)	$ (372,612)

Financings - Additional Informa

Financings - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Feb. 17, 2015	Feb. 09, 2015	Feb. 03, 2015	Oct. 29, 2013	Oct. 23, 2013
Class of Stock [Line Items]
Sale of stock price per share				$ 3.50
J.P. Morgan Securities Inc.
Class of Stock [Line Items]
Stock issued during period	1,500,000	10,000,000	10,000,000	2,145,000	14,300,000
Issuance & sale of common stock in public offering price per share			$ 8.75		$ 3.50
Option granted, exercisable period			30 days		30 days
Sale of stock price per share			$ 8.225		$ 3.29
Net proceeds from issuance of common stock	$ 94.3
Option to purchase common stock			1,500,000		2,145,000
Net proceeds from issuance of common stock				$ 53.9

Summary of Significant Accoun33

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Summary Of Significant Accounting Policies [Line Items]
Stock based compensation expenses	$ 7,997	$ 4,743	$ 3,507
Weighted average fair value of stock option granted	$ 10.47	$ 3.58	$ 2.51
Stock Options
Summary Of Significant Accounting Policies [Line Items]
Stock based compensation expenses	$ 5,300	$ 3,700	$ 2,300
Restricted Stock
Summary Of Significant Accounting Policies [Line Items]
Stock based compensation expenses	2,700	1,000	1,200
Employee and Director Awards
Summary Of Significant Accounting Policies [Line Items]
Stock based compensation expenses	8,000	$ 4,700	$ 3,500
Other Noncurrent Assets | Lease Obligations
Summary Of Significant Accounting Policies [Line Items]
Restricted cash	388
Other Noncurrent Assets | Line of Credit
Summary Of Significant Accounting Policies [Line Items]
Restricted cash	$ 104
Minimum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life	3 years
Maximum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life	5 years

Assets and Liabilities Measured

Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 137,405	$ 37,290
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 137,405	$ 37,290

Stock-Based Compensation Expens

Stock-Based Compensation Expense Included in Statement of Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 7,997	$ 4,743	$ 3,507
Income tax benefit	0	0	0
Net share based employee compensation expense	7,997	4,743	3,507
Research and Development Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	1,403	1,416	792
General and Administrative Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 6,594	$ 3,327	$ 2,715

Fair Value of Stock Options Ass

Fair Value of Stock Options Assumptions Using Black-Scholes Option Valuation Model (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, Minimum	1.46%	1.74%	1.00%
Risk-free interest rate, Maximum	1.93%	2.11%	2.10%
Expected life in years	6 years	6 years	6 years
Expected volatility, Minimum	79.13%	85.22%	83.40%
Expected volatility, Maximum	86.81%	94.55%	95.96%
Expected dividend yield	0.00%	0.00%	0.00%

Potentially Dilutive Shares Exc

Potentially Dilutive Shares Excluded from Computation of Diluted Net Loss Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	5,067,856	6,650,172	17,639,935
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	3,481,468	6,505,664	6,747,303
Restricted Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	1,586,388	144,508	352,865
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount			10,539,767

Restructuring - Additional Info

Restructuring - Additional Information (Detail) $ in Thousands	May. 22, 2015USD ($)	Oct. 17, 2013ft²	Aug. 30, 2013ft²	Dec. 31, 2015USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2014USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring charges					$ 1,700
Loss on disposition of business					(800)
Loss on disposal of fixed assets					(600)
Loss on disposal of fixed assets					(585)
Expected sublease revenue from subtenant for next year				$ 962
Boston, MA
Restructuring Cost and Reserve [Line Items]
Area under sublease agreement | ft²			5,249
Loss on sublease					42
Remaining contractual obligation					367
Sublease revenue from subtenant	$ 105				325
Loss on disposal of fixed assets					(194)
Security deposits	$ 17			$ 127	20			$ 127
Date of sublease vacated for lease				2014-10
Operating lease expiration month and year	2016-08						2016-08
Expected sublease revenue from subtenant for next year				$ 44
New York, NY
Restructuring Cost and Reserve [Line Items]
Area under sublease agreement | ft²		7,259
Loss on sublease					729
Remaining contractual obligation					2,300
Sublease revenue from subtenant					1,600
Loss on disposal of fixed assets					(392)
Operating lease expiration month and year						2018-10
General and Administrative Expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges					600
Research and Development Expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges					$ 1,100

Component of Property and Equip

Component of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Office and computer equipment	$ 1,105	$ 1,094
Software	886	874
Leasehold improvements	990	927
Manufacturing equipment	572	251
Property and equipment, Gross	3,553	3,146
Less: accumulated depreciation	(2,972)	(2,615)
Property and equipment, net	$ 581	$ 531

Property and Equipment, net - A

Property and Equipment, net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 357	$ 462	$ 738

Component of Accrued Expenses (

Component of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Accrued Liabilities [Line Items]
Clinical consulting services	$ 2,331	$ 2,802
Preclinical services	3,976	2,027
Employee compensation	1,453	768
Professional services	317	422
Payroll taxes and benefits	289	417
Manufacturing services	253	308
Accrued vacation	221	212
Other consulting services	66	226
Total	$ 8,906	$ 7,182

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($)	Jan. 08, 2016	Sep. 28, 2015	Jun. 29, 2015	Mar. 27, 2015	Feb. 03, 2015	Jan. 13, 2015	Jan. 06, 2011	Jul. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Related Party Transaction [Line Items]
Commitment to purchase common stock									$ 34,000
Research and Development Expense									106,785,000	$ 32,706,000	$ 42,852,000
Research and Development Service Agreement Aggregate Quarterly Payments									11,250,000
Stock buy back									34,000
Company purchased remaining shares Value									518,000	544,000	498,000
Minimum
Related Party Transaction [Line Items]
Research and Development Expense						$ 15,000,000
License Agreement
Related Party Transaction [Line Items]
Research and Development Expense									$ 67,300,000
Issuance of common stock in licensing agreement (in shares)						11,722,163			11,722,163
M.D. Anderson Cancer Center | Minimum
Related Party Transaction [Line Items]
Ownership percentage									5.00%
Intrexon Corporation
Related Party Transaction [Line Items]
Commitment to purchase common stock				$ 43,500,000			$ 50,000,000
Percentage of commitment for payments from receipts of upfronts, milestones and royalties				50.00%
Stock issued during period					1,440,000
Stock buy back (Shares)			3,711
Stock buy back			$ 34,000
Share buy back discount on closing price			5.00%
Amounts paid for services incurred									$ 16,300,000	12,000,000	$ 7,800,000
Amount due to related party, current									$ 4,600,000	$ 1,900,000
Licensing fee		$ 10,000,000						$ 115,000,000
Intrexon Corporation | Subsequent Event
Related Party Transaction [Line Items]
Company purchased remaining shares	168
Company purchased remaining shares Value	$ 2,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	Nov. 12, 2015USD ($)	Sep. 28, 2015USD ($)	May. 22, 2015USD ($)	Jan. 13, 2015USD ($)shares	Jan. 09, 2015USD ($)shares	Mar. 07, 2011USD ($)	Jan. 06, 2011	Aug. 24, 2004Patent	Jul. 31, 2015USD ($)	Dec. 31, 2015USD ($)	Sep. 30, 2015USD ($)	Jun. 30, 2015USD ($)	Mar. 31, 2015USD ($)	Dec. 31, 2014USD ($)shares	Sep. 30, 2014USD ($)	Jun. 30, 2014USD ($)	Mar. 31, 2014USD ($)	Dec. 31, 2015USD ($)Agreementshares	Dec. 31, 2014USD ($)shares	Dec. 31, 2013USD ($)	Dec. 31, 2012	Dec. 31, 2011USD ($)	Mar. 31, 2016$ / sharesshares	May. 31, 2015USD ($)	Oct. 29, 2013$ / shares	Nov. 02, 2012USD ($)
Commitments and Contingencies Disclosure [Line Items]
Loss on disposal of fixed assets																				$ (585,000)
Total rent Expense																		$ 1,000,000	$ 1,200,000	1,000,000
Deferred rent - current portion										$ 348,000				$ 280,000				348,000	280,000
Deferred rent-non-current portion										313,000				570,000				313,000	570,000
Deferred rent liability net										661,000				850,000				661,000	850,000
Research and Development Expense																		106,785,000	32,706,000	42,852,000
Research and development arrangement Terms				Pursuant to the Research and Development Agreement, the Company, Intrexon and MD Anderson have agreed to form a joint steering committee that will oversee and manage the new and ongoing research programs. As provided under the MD Anderson License, the Company will provide funding for research and development activities in support of the research programs under the Research and Development Agreement for a period of three years and in an amount of no less than $15 million and no greater than $20 million per year.
Research and Development Service Agreement Aggregate Quarterly Payments																		11,250,000
Offset costs in research and development expense																		911,000
Deferred revenue - current portion										6,861,000				1,360,000				6,861,000	1,360,000
Deferred Revenue, long term										47,917,000								47,917,000
Sale of stock price per share | $ / shares																									$ 3.50
Research contract revenue										1,919,000	$ 1,869,000	$ 272,000	$ 272,000	340,000	$ 633,000	$ 200,000	$ 200,000	4,332,000	1,373,000	800,000
DEKK Tec Inc | Scenario, Forecast
Commitments and Contingencies Disclosure [Line Items]
Sale of stock price per share | $ / shares																							$ 0.02
Outstanding options to purchase common stock | shares																							13,808
Southern Research Institute
Commitments and Contingencies Disclosure [Line Items]
Royalty payment																		$ 25,000	25,000	25,000
The University of Texas MD Anderson Cancer Center and The Texas A & M University System
Commitments and Contingencies Disclosure [Line Items]
Milestone maximum payment														$ 4,500,000					$ 4,500,000
Number of products | Patent								2
Options to purchase common stock | shares																		50,222
The University of Texas MD Anderson Cancer Center and The Texas A & M University System | Upon enrollment of the first patient in a multi-center pivotal clinical trial
Commitments and Contingencies Disclosure [Line Items]
Shares expected to vest | shares														12,556					12,556
Solasia
Commitments and Contingencies Disclosure [Line Items]
Upfront payment received						$ 5,000,000
Deferred revenue - current portion										272,000								$ 272,000
Research contract revenue																		$ 1,100,000
Estimated upfront payment for research and development funding earning period																		75 months
Solasia | Development-based milestones
Commitments and Contingencies Disclosure [Line Items]
Expected Additional milestone payments to be received																		$ 32,500,000
Solasia | Sales-based milestones
Commitments and Contingencies Disclosure [Line Items]
Expected Additional milestone payments to be received																		$ 53,500,000
Novella Clinical, Inc.
Commitments and Contingencies Disclosure [Line Items]
Milestone maximum payment																										$ 790,000
Number of amendments signed | Agreement																		2
Novella Clinical, Inc. | Upon three clinical milestones
Commitments and Contingencies Disclosure [Line Items]
Installment payments													$ 10,000						$ 236,000
Baxter Healthcare Corporation | Upon the successful U.S. IND application for indibulin
Commitments and Contingencies Disclosure [Line Items]
Installment payments																		$ 250,000	250,000	250,000
Predictive Therapeutics, Ltd.
Commitments and Contingencies Disclosure [Line Items]
Upfront payment received																		250,000
Deferred revenue - current portion										200,000								200,000
Research contract revenue																		50,000
Predictive Therapeutics, Ltd. | Development Regulatory And Sales Based Milestone
Commitments and Contingencies Disclosure [Line Items]
Upfront payment received	$ 250,000
Expected Additional milestone payments to be received																		12,800,000
License Agreement
Commitments and Contingencies Disclosure [Line Items]
Research and Development Expense																		$ 67,300,000
Issuance of common stock in licensing agreement, shares | shares				11,722,163														11,722,163
ARES Trading License
Commitments and Contingencies Disclosure [Line Items]
Agreement termination, notice period																		90 days
Payments for development and commercial milestones per Product																		$ 413,000,000
Milestone payments, percentage																		50.00%
Agreement commencement date																		2015-05
Deferred revenue, revenue recognized																		$ 3,200,000
Deferred revenue, upfront payment										54,300,000								54,300,000						$ 57,500,000
Minimum
Commitments and Contingencies Disclosure [Line Items]
Research and Development Expense				$ 15,000,000
Maximum
Commitments and Contingencies Disclosure [Line Items]
Research and Development Expense				20,000,000
Prepaid Expenses and Other Current Assets
Commitments and Contingencies Disclosure [Line Items]
Pre paid research and development expenses										10,300,000								$ 10,300,000
Intrexon Corporation
Commitments and Contingencies Disclosure [Line Items]
Contract termination description																		The Company's obligation to pay 50% of net profits or revenue described above with respect to these "retained" products will survive termination of the Channel Agreement.
Licensing fee		$ 10,000,000							$ 115,000,000
Milestone payment receivable																		$ 5,000,000
Milestone payment receivable period																		2 years
Upfront payment received									$ 57,500,000
Percentage of upfront fee Payable									50.00%
Milestone maximum payment										50,000,000								$ 50,000,000
Intrexon Corporation | GVHDA Arrangement
Commitments and Contingencies Disclosure [Line Items]
Percent of company net profit																		50.00%
Contract termination description																		The Company's obligation to pay 50% of net profits or revenue with respect to these "retained" products will survive termination of the GvHD Agreement.
Licensing fee		$ 10,000,000
Agreement termination period		24 months
Agreement termination, notice period		90 days
Research and Development Expense																		$ 10,000,000
Intrexon Corporation | License Agreement
Commitments and Contingencies Disclosure [Line Items]
Cash consideration for license agreement				$ 50,000,000
Intrexon Corporation | Letter Agreement
Commitments and Contingencies Disclosure [Line Items]
Cash consideration for license agreement					$ 7,500,000
Intrexon Corporation | Quarterly Payment
Commitments and Contingencies Disclosure [Line Items]
Percent of company net profit							50.00%
Percentage of revenue agreed to pay which is obtained from sublicensor							50.00%
ZIOPHARM | License Agreement
Commitments and Contingencies Disclosure [Line Items]
Common stock issued for cash | shares				10,124,561
Cash consideration for license agreement				$ 50,000,000
ZIOPHARM | Letter Agreement
Commitments and Contingencies Disclosure [Line Items]
Common stock issued for cash | shares					1,597,602
Cash consideration for license agreement					$ 7,500,000
New York, NY
Commitments and Contingencies Disclosure [Line Items]
Letter of credit										388,000								388,000				$ 388,000
Operating lease expiration month and year																					2018-10
Loss on sublease																				729,000
Remaining contractual obligation																				2,300,000
Sublease revenue from subtenant																				1,600,000
Loss on disposal of fixed assets																				(392,000)
Boston, MA
Commitments and Contingencies Disclosure [Line Items]
Operating lease expiration month and year			2016-08																			2016-08
Loss on sublease																				42,000
Remaining contractual obligation																				367,000
Sublease revenue from subtenant			$ 105,000																	325,000
Loss on disposal of fixed assets																				(194,000)
Security deposits			$ 17,000							$ 127,000				$ 127,000				127,000	127,000	$ 20,000
Security deposit from subtenant														$ 20,000					$ 20,000
Boston, MA | The first floor
Commitments and Contingencies Disclosure [Line Items]
Loss on sublease																		$ 167,000

Future Minimum Lease Payments u

Future Minimum Lease Payments under Operating Leases (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Operating Leased Assets [Line Items]
2,016	$ 1,139
2,017	928
2,018	851
2,019	427
2020 and beyond	712
Operating Leases, Future Minimum Payments Due, Total	4,057
Less: contractual sublease income	(962)
Future minimum lease payments, net	$ 3,095

Warrants - Additional Informati

Warrants - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Oct. 31, 2009	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2009
Class of Warrant or Right [Line Items]
Warrants to purchase an aggregate of shares of common stock					8,206,520
Warrant term					5 years
Warrants expiration date		2014-12
Other income (expense), net		$ 12	$ (5)	$ (579)
Gain on expiration of liability-classified warrants			$ 195
Warrants exercised			4,004,907	135,346
Conversion of Warrants to Common Stock			3,725,277	112,808
Liability
Class of Warrant or Right [Line Items]
Classified warrants				$ 11,800
Warrants outstanding			1,755,845	0
Warrants expired			6,479,231
Equity
Class of Warrant or Right [Line Items]
Warrants outstanding			2,249,062	135,346
Warrants expired			12,329
Liability Warrants
Class of Warrant or Right [Line Items]
Other income (expense), net				$ (1,200)
Private Placement
Class of Warrant or Right [Line Items]
Warrants to purchase an aggregate of shares of common stock					2,910,954
Warrant exercise price					$ 2.04
Warrant exercisable Period					5 years
Estimated fair value of warrant					$ 4,200
Warrants exercised	136,986
Private Placement | Warrants
Class of Warrant or Right [Line Items]
Expected volatility					105.00%
Risk-free interest rate					2.41%
Expected life in years					5 years
Expected dividend yield					0.00%
J. P. Morgan Securities LLC
Class of Warrant or Right [Line Items]
Warrants issued					464,520
Placement Agents | Private Placement
Class of Warrant or Right [Line Items]
Warrants to purchase an aggregate of shares of common stock					138,617

Assumptions Used In Binomial Va

Assumptions Used In Binomial Valuation Model and Black-Scholes Valuation Model (Detail) - Black Scholes Option Pricing Model - Warrants	12 Months Ended
	Dec. 31, 2013
Class of Warrant or Right [Line Items]
Risk-free interest rate	0.13%
Expected life in years	11 months 9 days
Expected volatility	80.00%
Expected dividend yield	0.00%

Significant Component of Deferr

Significant Component of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred Tax Assets [Line Items]
Net operating loss carryforwards	$ 96,215	$ 79,050
Start-up and organizational costs	64,942	38,562
Research and development credit carryforwards	29,564	26,112
Stock compensation	1,997	1,181
Capitalized acquisition costs	10,429	11,376
Deferred revenue	2,695	534
Depreciation	251	208
Other	1,673	1,547
Deferred Tax Assets Gross	207,766	158,570
Less valuation allowance	(207,766)	(158,570)
Effective tax rate	$ 0	$ 0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Line Items]
Net operating loss carryforwards	$ 96,215	$ 79,050
Research and development credit carryforwards	29,564	26,112
Net Operating loss Carryforwards resulting from excess tax deduction	10,200
Increase (decrease) in valuation allowance	49,200
Net Operating Loss Carryforwards
Income Taxes [Line Items]
Increase (decrease) in deferred tax assets		(11,200)
General Business Credits
Income Taxes [Line Items]
Increase (decrease) in deferred tax assets		$ (636)
Federal
Income Taxes [Line Items]
Net operating loss carryforwards	$ 251,000
Net operating loss carryforwards, expiration date	2,034
Research and Development Credit
Income Taxes [Line Items]
Net operating loss carryforwards, expiration date	2,034
Research and development credit carryforwards	$ 29,000

Reconciliation of Income Tax Ex

Reconciliation of Income Tax Expense (Benefit) (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of Effective Tax Rate [Line Items]
Federal income tax at statutory rates	34.00%	34.00%	34.00%
State income tax, net of federal tax benefit	5.00%	2.00%	4.00%
Research and development credits	3.00%	3.00%	9.00%
Stock compensation	(1.00%)	(4.00%)	(2.00%)
Other	0.00%	(4.00%)	1.00%
Increase in valuation allowance	(41.00%)	(31.00%)	(46.00%)
Effective tax rate	0.00%	0.00%	0.00%

Summary of Adjustments to Uncer

Summary of Adjustments to Uncertain Tax Position (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Contingency [Line Items]
Beginning Balance	$ 238	$ 238	$ 275
Increase/Decrease for tax positions related to the current year	0	0	0
Increase/Decrease for tax positions related to prior years			(37)
Decrease for settlements with applicable taxing authorities	0	0	0
Decrease for previous year's lapses of statute of limitations	(20)
Decrease for impact of §382 limitations	(218)
Decrease for lapses of statute of limitations	$ 0	0	0
Ending Balance		$ 238	$ 238

Preferred Stock and Stockhold51

Preferred Stock and Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Feb. 17, 2015	Feb. 09, 2015	Feb. 03, 2015	Jan. 13, 2015	Oct. 29, 2013	Oct. 23, 2013	Dec. 31, 2015	Dec. 31, 2013	Dec. 31, 2014	Apr. 26, 2006
Equity [Line Items]
Shares of authorized capital stock										280,000,000
Common stock, shares authorized							250,000,000		250,000,000	250,000,000
Common stock par value per share							$ 0.001		$ 0.001	$ 0.001
Preferred stock, shares authorized										30,000,000
Preferred stock par value										$ 0.001
Common Stock Shares Sold					16,445,000
Proceeds from issuance of common stock					$ 57,600		$ 94,320	$ 53,880
Common Stock Price Per Share					$ 3.50
License Agreement
Equity [Line Items]
Issuance of common stock in licensing agreement (in shares)				11,722,163			11,722,163
J.P. Morgan Securities Inc.
Equity [Line Items]
Common Stock Price Per Share			$ 8.225			$ 3.29
Stock issued during period	1,500,000	10,000,000	10,000,000		2,145,000	14,300,000
Issuance & sale of common stock in public offering price per share			$ 8.75			$ 3.50
Option granted, exercisable period			30 days			30 days
Option to purchase common stock			1,500,000			2,145,000
Expected net proceeds from issuance of common stock	$ 94,300

Stock Option Plan - Additional

Stock Option Plan - Additional information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended											12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	May. 31, 2015	Dec. 31, 2014	Feb. 28, 2014	Jan. 31, 2014	Dec. 31, 2013	May. 31, 2013	Mar. 31, 2013	Jan. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jun. 18, 2014	May. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance	26,364											26,364
Outstanding options issued	3,481,469				6,505,664			6,747,303				3,481,469	6,505,664	6,747,303	7,147,303
Proceeds from stock options exercised												$ 4,568	$ 1,386	$ 956
Total intrinsic value of options												23,800	$ 2,600	$ 1,400
Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period															3 years
Contractual terms															10 years
Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual terms															10 years
Director | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period															3 years
Director | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period															1 year
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Repurchase of shares of restricted common stock	16,709	7,669			81,702	14,600	16,031	56,683	2,623	5,400	52,018
Repurchase of shares of restricted common stock, price per share	$ 8.31	$ 11.57			$ 5.04	$ 4.40	$ 4.37	$ 4.37	$ 1.65	$ 4.50	$ 4.28
Restricted Stock | Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years		3 years	3 years
Share-based payment award granted	403,083		50,000	1,000,000
Restricted Stock | Non Employee Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	1 year				1 year			1 year
Share-based payment award granted	133,305	4,186			66,828			75,272
Non Vested Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs related to non-vested restricted stock outstanding	$ 5,300											$ 5,300
Expected recognition period												1 year 6 months 18 days
Unvested Restricted Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected recognition period												1 year 8 months 23 days
Share-based payment award granted												1,590,574	66,828	75,272
Unrecognized stock-based compensation expense related to non-vested restricted stock arrangements	$ 12,100											$ 12,100
the "2012 Plan"
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance	9,000,000											9,000,000				5,000,000	4,000,000
the "2012 Plan" | Employees | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding options issued	2,420,801											2,420,801
the "2012 Plan" | Director | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding options issued	927,500											927,500
the "2012 Plan" | Consultants | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding options issued	133,167											133,167

Stock Option Activity Under Sto

Stock Option Activity Under Stock Option Plan (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Number of Shares
Beginning Balance	6,505,664	6,747,303	7,147,303
Granted	427,800	1,099,300	2,649,900
Exercised	(3,249,160)	(613,138)	(570,168)
Cancelled	(202,835)	(727,801)	(2,479,732)
Ending Balance	3,481,469	6,505,664	6,747,303
Vested and unvested expected to vest at end of period	3,443,414
Weighted Average Exercise Price
Beginning Balance	$ 4.07	$ 3.81	$ 4.11
Granted	10.47	4.95	3.28
Exercised	3.95	2.26	1.68
Cancelled	4.36	4.54	4.58
Ending Balance	$ 4.96	$ 4.07	$ 3.81
Options exercisable, at end of period	2,120,834	3,781,162
Options available for future grant	2,768,230
Vested and unvested expected to vest at end of period	$ 4.24
Options exercisable, at end of period	$ 4.24	$ 4.10
Weighted Average Contractual Term (Years)
Outstanding, at end of period	6 years 11 months 23 days
Vested and unvested expected to vest at end of period	5 years 10 months 2 days
Options exercisable, at end of period	5 years 10 months 2 days	5 years 9 months 18 days
Aggregate Intrinsic Value
Outstanding, at end of period	$ 12,601
Vested and unvested expected to vest at end of period	12,463
Options exercisable, at end of period	$ 8,622	$ 4,130

Summary of Unvested Restricted

Summary of Unvested Restricted Stock (Detail) - Unvested Restricted Common Stock - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Number of Shares
Beginning Balance	144,508	352,865	733,739
Granted	1,590,574	66,828	75,272
Vested	(148,694)	(253,835)	(292,399)
Cancelled		(21,350)	(163,747)
Ending Balance	1,586,388	144,508	352,865
Weighted Average Grant Date Fair Value
Beginning Balance	$ 4.70	$ 4.38	$ 4.37
Granted	9.01	5.07	4.34
Vested	4.88	4.38	4.31
Cancelled		4.41	4.42
Ending Balance	$ 9	$ 4.70	$ 4.38

Employee Benefit Plan - Additio

Employee Benefit Plan - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan contributions by employer	$ 47	$ 79	$ 139

Selected Quarterly Informatio56

Selected Quarterly Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information [Line Items]
Revenue	$ 1,919	$ 1,869	$ 272	$ 272	$ 340	$ 633	$ 200	$ 200	$ 4,332	$ 1,373	$ 800
Total operating expenses	11,401	20,035	14,497	78,499	10,936	12,575	11,377	9,984	124,432	44,872	58,513
Loss from operations	(9,482)	(18,166)	(14,225)	(78,227)	(10,596)	(11,942)	(11,177)	(9,784)	(120,100)	(43,499)	(57,713)
Change in fair value of warrants					194	5,847	5,600	82		11,723	1,185
Net (loss)	$ (9,476)	$ (18,170)	$ (14,211)	$ (78,231)	$ (10,401)	$ (6,093)	$ (5,576)	$ (9,711)	$ (120,088)	$ (31,781)	$ (57,107)
Loss per share, basic and diluted	$ (0.07)	$ (0.14)	$ (0.11)	$ (0.69)	$ (0.09)	$ (0.06)	$ (0.06)	$ (0.10)	$ (0.96)	$ (0.31)	$ (0.66)